[chromeos/about:power] Collect cpuidle and cpufreq stats

chrome/browser/resources/chromeos/power.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * Plot a line graph of data versus time on a HTML canvas element.
  *
- * @param {HTMLCanvasElement} canvas The canvas on which the line graph is
+ * @param {HTMLCanvasElement} plotCanvas The canvas on which the line graph is
  *     drawn.
+ * @param {HTMLCanvasElement} legendCanvas The canvas on which the legend for
+ *     the line graph is drawn.
  * @param {Array.<number>} tData The time (in seconds) in the past when the
  *     corresponding data in plots was sampled.
  * @param {Array.<{data: Array.<number>, color: string}>} plots An
  *     array of plots to plot on the canvas. The field 'data' of a plot is an
  *     array of samples to be plotted as a line graph with color speficied by
  *     the field 'color'. The elements in the 'data' array are ordered
  *     corresponding to their sampling time in the argument 'tData'. Also, the
  *     number of elements in the 'data' array should be the same as in the time
  *     array 'tData' above.
  * @param {number} yMin Minimum bound of y-axis
  * @param {number} yMax Maximum bound of y-axis.
  * @param {integer} yPrecision An integer value representing the number of
  *     digits of precision the y-axis data should be printed with.
  */
-function plotLineGraph(canvas, tData, plots, yMin, yMax, yPrecision) {
+function plotLineGraph(
+    plotCanvas, legendCanvas, tData, plots, yMin, yMax, yPrecision) {
   var textFont = '12px Arial';
   var textHeight = 12;
   var padding = 5;  // Pixels
   var errorOffsetPixels = 15;
   var gridColor = '#ccc';
-  var ctx = canvas.getContext('2d');
+  var plotCtx = plotCanvas.getContext('2d');
   var size = tData.length;
 
-  function drawText(text, x, y) {
+  function drawText(ctx, text, x, y) {
     ctx.font = textFont;
     ctx.fillStyle = '#000';
     ctx.fillText(text, x, y);
   }
 
-  function printErrorText(text) {
-    ctx.clearRect(0, 0, canvas.width, canvas.height);
-    drawText(text, errorOffsetPixels, errorOffsetPixels);
+  function printErrorText(ctx, text) {
+    ctx.clearRect(0, 0, plotCanvas.width, plotCanvas.height);
+    drawText(ctx, text, errorOffsetPixels, errorOffsetPixels);
   }
 
   if (size < 2) {
-    printErrorText(loadTimeData.getString('notEnoughDataAvailableYet'));
+    printErrorText(plotCtx,
+                   loadTimeData.getString('notEnoughDataAvailableYet'));
     return;
   }
 
   for (var count = 0; count < plots.length; count++) {
     if (plots[count].data.length != size) {
       throw new Error('Mismatch in time and plot data.');
     }
   }
 
   function valueToString(value) {
-    return Number(value).toPrecision(yPrecision);
+    if (Math.abs(value) < 1) {
+      return Number(value).toFixed(yPrecision - 1);
+    } else {
+      return Number(value).toPrecision(yPrecision);
+    }
   }
 
-  function getTextWidth(text) {
+  function getTextWidth(ctx, text) {
     ctx.font = textFont;
     // For now, all text is drawn to the left of vertical lines, or centered.
     // Add a 2 pixel padding so that there is some spacing between the text
     // and the vertical line.
     return Math.round(ctx.measureText(text).width) + 2;
   }
 
-  function drawHighlightText(text, x, y, color) {
+  function drawHighlightText(ctx, text, x, y, color) {
     ctx.strokeStyle = '#000';
-    ctx.strokeRect(x, y - textHeight, getTextWidth(text), textHeight);
+    ctx.strokeRect(x, y - textHeight, getTextWidth(ctx, text), textHeight);
     ctx.fillStyle = color;
-    ctx.fillRect(x, y - textHeight, getTextWidth(text), textHeight);
+    ctx.fillRect(x, y - textHeight, getTextWidth(ctx, text), textHeight);
     ctx.fillStyle = '#fff';
     ctx.fillText(text, x, y);
   }
 
-  function drawLine(x1, y1, x2, y2, color) {
+  function drawLine(ctx, x1, y1, x2, y2, color) {
     ctx.save();
     ctx.beginPath();
     ctx.moveTo(x1, y1);
     ctx.lineTo(x2, y2);
     ctx.strokeStyle = color;
     ctx.stroke();
     ctx.restore();
   }
 
-  // The strokeRect method of the 2d context of a canvas draws a bounding
+  // The strokeRect method of the 2d context of a plotCanvas draws a bounding
   // rectangle with an offset origin and greater dimensions. Hence, use this
   // function to draw a rect at the desired location with desired dimensions.
-  function drawRect(x, y, width, height, color) {
-    drawLine(x, y, x + width - 1, y, color);
-    drawLine(x, y, x, y + height - 1, color);
-    drawLine(x, y + height - 1, x + width - 1, y + height - 1, color);
-    drawLine(x + width - 1, y, x + width - 1, y + height - 1, color);
+  function drawRect(ctx, x, y, width, height, color) {
+    drawLine(ctx, x, y, x + width - 1, y, color);
+    drawLine(ctx, x, y, x, y + height - 1, color);
+    drawLine(ctx, x, y + height - 1, x + width - 1, y + height - 1, color);
+    drawLine(ctx, x + width - 1, y, x + width - 1, y + height - 1, color);
+  }
+
+  function drawLegend() {
+    // Show a legend only if atleast one individual plot have a name.

[arv (Not doing code reviews), 2014/03/10 17:00:46]

at least

[Siva Chandra, 2014/03/10 18:46:09]

Done.

+    var valid = false;
+    for (var i = 0; i < plots.length; i++) {
+      if (plots[i].name != null) {
+        valid = true;
+        break;
+      }
+    }
+    if (!valid) {
+      legendCanvas.hidden = true;
+      return;
+    }
+
+    var padding = 2;
+    var legendSquareSide = 12;
+    var legendCtx = legendCanvas.getContext('2d');
+    var xLoc = padding;
+    var yLoc = padding;
+    // Adjust the height of the canvas before drawing on it.
+    for (var i = 0; i < plots.length; i++) {
+      if (plots[i].name == null) {
+        continue;
+      }
+      var legendText = '  -  ' + plots[i].name;
+      xLoc += legendSquareSide + getTextWidth(legendCtx, legendText) +
+              2 * padding;
+      if (i < plots.length - 1) {
+        var xLocNext = xLoc +
+                       getTextWidth(legendCtx, '  -  ' + plots[i + 1].name) +
+                       legendSquareSide;
+        if (xLocNext >= legendCanvas.width) {
+          xLoc = padding;
+          yLoc = yLoc + 2 * padding + textHeight;
+        }
+      }
+    }
+
+    legendCanvas.height = yLoc + textHeight + padding;
+
+    xLoc = padding;
+    yLoc = padding;
+    // Go over the plots again, this time drawing the legends.
+    for (var i = 0; i < plots.length; i++) {
+      legendCtx.fillStyle = plots[i].color;
+      legendCtx.fillRect(xLoc, yLoc, legendSquareSide, legendSquareSide);
+      xLoc += legendSquareSide;
+
+      var legendText = '  -  ' + plots[i].name;
+      drawText(legendCtx, legendText, xLoc, yLoc + textHeight - 1);
+      xLoc += getTextWidth(legendCtx, legendText) + 2 * padding;
+
+      if (i < plots.length - 1) {
+        var xLocNext = xLoc +
+                       getTextWidth(legendCtx, '  -  ' + plots[i + 1].name) +
+                       legendSquareSide;
+        if (xLocNext >= legendCanvas.width) {
+          xLoc = padding;
+          yLoc = yLoc + 2 * padding + textHeight;
+        }
+      }
+    }
   }
 
   var yMinStr = valueToString(yMin);
   var yMaxStr = valueToString(yMax);
   var yHalfStr = valueToString((yMax + yMin) / 2);
-  var yMinWidth = getTextWidth(yMinStr);
-  var yMaxWidth = getTextWidth(yMaxStr);
-  var yHalfWidth = getTextWidth(yHalfStr);
+  var yMinWidth = getTextWidth(plotCtx, yMinStr);
+  var yMaxWidth = getTextWidth(plotCtx, yMaxStr);
+  var yHalfWidth = getTextWidth(plotCtx, yHalfStr);
 
   var xMinStr = tData[0];
   var xMaxStr = tData[size - 1];
-  var xMinWidth = getTextWidth(xMinStr);
-  var xMaxWidth = getTextWidth(xMaxStr);
+  var xMinWidth = getTextWidth(plotCtx, xMinStr);
+  var xMaxWidth = getTextWidth(plotCtx, xMaxStr);
 
   var xOrigin = padding + Math.max(yMinWidth,
                                    yMaxWidth,
                                    Math.round(xMinWidth / 2));
   var yOrigin = padding + textHeight;
-  var width = canvas.width - xOrigin - Math.floor(xMaxWidth / 2) - padding;
+  var width = plotCanvas.width - xOrigin - Math.floor(xMaxWidth / 2) - padding;
   if (width < size) {
-    canvas.width += size - width;
+    plotCanvas.width += size - width;
     width = size;
   }
-  var height = canvas.height - yOrigin - textHeight - padding;
+  var height = plotCanvas.height - yOrigin - textHeight - padding;
 
   function drawPlots() {
     // Start fresh.
-    ctx.clearRect(0, 0, canvas.width, canvas.height);
+    plotCtx.clearRect(0, 0, plotCanvas.width, plotCanvas.height);
 
     // Draw the bounding rectangle.
-    drawRect(xOrigin, yOrigin, width, height, gridColor);
+    drawRect(plotCtx, xOrigin, yOrigin, width, height, gridColor);
 
     // Draw the x and y bound values.
-    drawText(yMaxStr, xOrigin - yMaxWidth, yOrigin + textHeight);
-    drawText(yMinStr, xOrigin - yMinWidth, yOrigin + height);
-    drawText(xMinStr, xOrigin - xMinWidth / 2, yOrigin + height + textHeight);
-    drawText(xMaxStr,
+    drawText(plotCtx, yMaxStr, xOrigin - yMaxWidth, yOrigin + textHeight);
+    drawText(plotCtx, yMinStr, xOrigin - yMinWidth, yOrigin + height);
+    drawText(plotCtx,
+             xMinStr,
+             xOrigin - xMinWidth / 2,
+             yOrigin + height + textHeight);
+    drawText(plotCtx,
+             xMaxStr,
              xOrigin + width - xMaxWidth / 2,
              yOrigin + height + textHeight);
 
     // Draw y-level (horizontal) lines.
-    drawLine(xOrigin + 1, yOrigin + height / 4,
+    drawLine(plotCtx,
+             xOrigin + 1, yOrigin + height / 4,
              xOrigin + width - 2, yOrigin + height / 4,
              gridColor);
-    drawLine(xOrigin + 1, yOrigin + height / 2,
+    drawLine(plotCtx,
+             xOrigin + 1, yOrigin + height / 2,
              xOrigin + width - 2, yOrigin + height / 2, gridColor);
-    drawLine(xOrigin + 1, yOrigin + 3 * height / 4,
+    drawLine(plotCtx,
+             xOrigin + 1, yOrigin + 3 * height / 4,
              xOrigin + width - 2, yOrigin + 3 * height / 4,
              gridColor);
 
     // Draw half-level value.
-    drawText(yHalfStr,
+    drawText(plotCtx,
+             yHalfStr,
              xOrigin - yHalfWidth,
              yOrigin + height / 2 + textHeight / 2);
 
     // Draw the plots.
     var yValRange = yMax - yMin;
     for (var count = 0; count < plots.length; count++) {
       var plot = plots[count];
       var yData = plot.data;
-      ctx.strokeStyle = plot.color;
-      ctx.beginPath();
+      plotCtx.strokeStyle = plot.color;
+      plotCtx.beginPath();
       var beginPath = true;
       for (var i = 0; i < size; i++) {
         var val = yData[i];
         if (typeof val === 'string') {
           // Stroke the plot drawn so far and begin a fresh plot.
-          ctx.stroke();
-          ctx.beginPath();
+          plotCtx.stroke();
+          plotCtx.beginPath();
           beginPath = true;
           continue;
         }
         var xPos = xOrigin + Math.floor(i / (size - 1) * (width - 1));
         var yPos = yOrigin + height - 1 -
                    Math.round((val - yMin) / yValRange * (height - 1));
         if (beginPath) {
-          ctx.moveTo(xPos, yPos);
+          plotCtx.moveTo(xPos, yPos);
           // A simple move to does not print anything. Hence, draw a little
           // square here to mark a beginning.
-          ctx.fillStyle = '#000';
-          ctx.fillRect(xPos - 1, yPos - 1, 2, 2);
+          plotCtx.fillStyle = '#000';
+          plotCtx.fillRect(xPos - 1, yPos - 1, 2, 2);
           beginPath = false;
         } else {
-          ctx.lineTo(xPos, yPos);
+          plotCtx.lineTo(xPos, yPos);
           if (i === size - 1 || typeof yData[i + 1] === 'string') {
             // Draw a little square to mark an end to go with the start
             // markers from above.
-            ctx.fillStyle = '#000';
-            ctx.fillRect(xPos - 1, yPos - 1, 2, 2);
+            plotCtx.fillStyle = '#000';
+            plotCtx.fillRect(xPos - 1, yPos - 1, 2, 2);
           }
         }
       }
-      ctx.stroke();
+      plotCtx.stroke();
     }
 
     // Paint the missing time intervals with |gridColor|.
     // Pick one of the plots to look for missing time intervals.
+    function drawMissingRect(start, end) {
+      var xLeft = xOrigin + Math.floor(start / (size - 1) * (width - 1));
+      var xRight = xOrigin + Math.floor(end / (size - 1) * (width - 1));
+      plotCtx.fillStyle = gridColor;
+      // The x offsets below are present so that the blank space starts
+      // and ends between two valid samples.
+      plotCtx.fillRect(xLeft + 1, yOrigin, xRight - xLeft - 2, height - 1);
+    }
     var inMissingInterval = false;
     var intervalStart;
     for (var i = 0; i < size; i++) {
       if (typeof plots[0].data[i] === 'string') {
         if (!inMissingInterval) {
           inMissingInterval = true;
           // The missing interval should actually start from the previous
           // sample.
           intervalStart = Math.max(i - 1, 0);
         }
+
+        if (i == size - 1) {
+          // If this is the last sample, just draw missing rect.
+          drawMissingRect(intervalStart, i);
+        }
       } else if (inMissingInterval) {
         inMissingInterval = false;
-        var xLeft = xOrigin +
-            Math.floor(intervalStart / (size - 1) * (width - 1));
-        var xRight = xOrigin + Math.floor(i / (size - 1) * (width - 1));
-        ctx.fillStyle = gridColor;
-        // The x offsets below are present so that the blank space starts
-        // and ends between two valid samples.
-        ctx.fillRect(xLeft + 1, yOrigin, xRight - xLeft - 2, height - 1);
+        drawMissingRect(intervalStart, i);
       }
     }
   }
 
   function drawTimeGuide(tDataIndex) {
     var x = xOrigin + tDataIndex / (size - 1) * (width - 1);
-    drawLine(x, yOrigin, x, yOrigin + height - 1, '#000');
-    drawText(tData[tDataIndex],
-             x - getTextWidth(tData[tDataIndex]) / 2,
+    drawLine(plotCtx, x, yOrigin, x, yOrigin + height - 1, '#000');
+    drawText(plotCtx,
+             tData[tDataIndex],
+             x - getTextWidth(plotCtx, tData[tDataIndex]) / 2,
              yOrigin - 2);
 
     for (var count = 0; count < plots.length; count++) {
       var yData = plots[count].data;
 
       // Draw small black square on the plot where the time guide intersects
       // it.
       var val = yData[tDataIndex];
       var yPos, valStr;
       if (typeof val === 'string') {
         yPos = yOrigin + Math.round(height / 2);
         valStr = val;
       } else {
         yPos = yOrigin + height - 1 -
             Math.round((val - yMin) / (yMax - yMin) * (height - 1));
         valStr = valueToString(val);
       }
-      ctx.fillStyle = '#000';
-      ctx.fillRect(x - 2, yPos - 2, 4, 4);
+      plotCtx.fillStyle = '#000';
+      plotCtx.fillRect(x - 2, yPos - 2, 4, 4);
 
       // Draw the val to right of the intersection.
       var yLoc;
       if (yPos - textHeight / 2 < yOrigin) {
         yLoc = yOrigin + textHeight;
       } else if (yPos + textHeight / 2 >= yPos + height) {
         yLoc = yOrigin + height - 1;
       } else {
         yLoc = yPos + textHeight / 2;
       }
-      drawHighlightText(valStr, x + 5, yLoc, plots[count].color);
+      drawHighlightText(plotCtx, valStr, x + 5, yLoc, plots[count].color);
     }
   }
 
   function onMouseOverOrMove(event) {
     drawPlots();
 
-    var boundingRect = canvas.getBoundingClientRect();
-    var x = event.clientX - boundingRect.left;
-    var y = event.clientY - boundingRect.top;
+    var boundingRect = plotCanvas.getBoundingClientRect();
+    var x = Math.round(event.clientX - boundingRect.left);
+    var y = Math.round(event.clientY - boundingRect.top);
     if (x < xOrigin || x >= xOrigin + width ||
         y < yOrigin || y >= yOrigin + height) {
       return;
     }
 
     if (width == size) {
       drawTimeGuide(x - xOrigin);
     } else {
       drawTimeGuide(Math.round((x - xOrigin) / (width - 1) * (size - 1)));
     }
   }
 
   function onMouseOut(event) {
     drawPlots();
   }
 
+  drawLegend();
   drawPlots();
-  canvas.addEventListener('mouseover', onMouseOverOrMove);
-  canvas.addEventListener('mousemove', onMouseOverOrMove);
-  canvas.addEventListener('mouseout', onMouseOut);
+  plotCanvas.addEventListener('mouseover', onMouseOverOrMove);
+  plotCanvas.addEventListener('mousemove', onMouseOverOrMove);
+  plotCanvas.addEventListener('mouseout', onMouseOut);
 }
 
 var sleepSampleInterval = 30 * 1000; // in milliseconds.
 var sleepText = loadTimeData.getString('systemSuspended');
+var invalidDataText = loadTimeData.getString('invalidData');
+var offlineText = loadTimeData.getString('offlineText');
+
+var plotColors = ['Red', 'Blue', 'Green', 'Gold', 'CadetBlue', 'LightCoral',
+                  'LightSlateGray', 'Peru', 'DarkRed', 'LawnGreen', 'Tan'];
+
+/**
+ * Add canvases for plotting to |plotsDiv|. For every header in |headerArray|,
+ * one canvas for the plot and one for its legend are added.
+ *
+ * @param {Array.<string>} headerArray Headers for the different plots to be
+ *     added to |plotsDiv|.
+ * @param {HTMLDivElement} plotsDiv The div element into which the canvases
+ *     are added.
+ * @return {<string>: {plotCanvas: <HTMLCanvasElement>,
+ *                     legendCanvas: <HTMLCanvasElement>} Returns an object
+ *    with the headers as 'keys'. Each element is an object containing the
+ *    legend canvas and the plot canvas that have been added to |plotsDiv|.
+ */
+function addCanvases(headerArray, plotsDiv) {
+  // Remove the contents before adding new ones.
+  while (plotsDiv.firstChild != null) {
+    plotsDiv.removeChild(plotsDiv.firstChild);
+  }
+  var width = Math.floor(plotsDiv.getBoundingClientRect().width);
+  var canvases = {};
+  for (var i = 0; i < headerArray.length; i++) {
+    var header = document.createElement('h4');
+    header.textContent = headerArray[i];
+    plotsDiv.appendChild(header);
+
+    var legendCanvas = document.createElement('canvas');
+    legendCanvas.width = width;
+    legendCanvas.height = 5;
+    plotsDiv.appendChild(legendCanvas);
+
+    var br = document.createElement('br');

[arv (Not doing code reviews), 2014/03/10 17:00:46]

I doubt this br is needed

[Siva Chandra, 2014/03/10 18:46:09]

Done.

+    plotsDiv.appendChild(br);
+
+    var plotCanvasDiv = document.createElement('div');
+    plotCanvasDiv.style.overflow = 'auto';
+    plotCanvasDiv.style.maxWidth = String(width) + 'px';
+    plotsDiv.appendChild(plotCanvasDiv);
+
+    plotCanvas = document.createElement('canvas');
+    plotCanvas.width = width;
+    plotCanvas.height = 200;
+    plotCanvasDiv.appendChild(plotCanvas);
+
+    canvases[headerArray[i]] = {plot: plotCanvas, legend: legendCanvas};
+  }
+  return canvases;
+}
 
 /**
  * Add samples in |sampleArray| to individual plots in |plots|. If the system
  * resumed from a sleep/suspend, then "suspended" sleep samples are added to
  * the plot for the sleep duration.
  *
  * @param {Array.<{data: Array.<number>, color: string}>} plots An
  *     array of plots to plot on the canvas. The field 'data' of a plot is an
  *     array of samples to be plotted as a line graph with color speficied by
  *     the field 'color'. The elements in the 'data' array are ordered
  *     corresponding to their sampling time in the argument 'tData'. Also, the
  *     number of elements in the 'data' array should be the same as in the time
  *     array 'tData' below.
  * @param {Array.<number>} tData The time (in seconds) in the past when the
  *     corresponding data in plots was sampled.
  * @param {Array.<number>} sampleArray The array of samples wherein each
  *     element corresponds to the individual plot in |plots|.
  * @param {number} sampleTime Time in milliseconds since the epoch when the
  *     samples in |sampleArray| were captured.
  * @param {number} previousSampleTime Time in milliseconds since the epoch
  *     when the sample prior to the current sample was captured.
  * @param {Array.<{time: number, sleepDuration: number}>} systemResumedArray An
  *     array objects corresponding to system resume events. The 'time' field is
  *     for the time in milliseconds since the epoch when the system resumed. The
  *     'sleepDuration' field is for the time in milliseconds the system spent
  *     in sleep/suspend state.
  */
-function addTimeDataSample(plots, tData, sampleArray,
+function addTimeDataSample(plots, tData, absTime, sampleArray,
                            sampleTime, previousSampleTime,
                            systemResumedArray) {
   for (var i = 0; i < plots.length; i++) {
     if (plots[i].data.length != tData.length) {
       throw new Error('Mismatch in time and plot data.');
     }
   }
 
   var time;
   if (tData.length == 0) {
     time = new Date(sampleTime);
+    absTime[0] = sampleTime;
     tData[0] = time.toLocaleTimeString();
     for (var i = 0; i < plots.length; i++) {
       plots[i].data[0] = sampleArray[i];
     }
     return;
   }
 
   for (var i = 0; i < systemResumedArray.length; i++) {
     var resumeTime = systemResumedArray[i].time;
     var sleepDuration = systemResumedArray[i].sleepDuration;
     var sleepStartTime = resumeTime - sleepDuration;
-    if (resumeTime < sampleTime && sleepStartTime > previousSampleTime) {
+    if (resumeTime < sampleTime) {
+      if (sleepStartTime < previousSampleTime) {
+        // This can happen if pending callbacks were handled before actually
+        // suspending.
+        sleepStartTime = previousSampleTime + 1000;
+      }
       // Add sleep samples for every |sleepSampleInterval|.
       var sleepSampleTime = sleepStartTime;
       while (sleepSampleTime < resumeTime) {
         time = new Date(sleepSampleTime);
+        absTime.push(sleepSampleTime);
         tData.push(time.toLocaleTimeString());
         for (var j = 0; j < plots.length; j++) {
           plots[j].data.push(sleepText);
         }
         sleepSampleTime += sleepSampleInterval;
       }
     }
   }
 
   time = new Date(sampleTime);
+  absTime.push(sampleTime);
   tData.push(time.toLocaleTimeString());
   for (var i = 0; i < plots.length; i++) {
     plots[i].data.push(sampleArray[i]);
   }
 }
 
 /**
  * Display the battery charge vs time on a line graph.
  *
  * @param {Array.<{time: number,
  *                 batteryPercent: number,
  *                 batteryDischargeRate: number,
  *                 externalPower: number}>} powerSupplyArray An array of objects
  *     with fields representing the battery charge, time when the charge
  *     measurement was taken, and whether there was external power connected at
  *     that time.
  * @param {Array.<{time: ?, sleepDuration: ?}>} systemResumedArray An array
  *     objects with fields 'time' and 'sleepDuration'. Each object corresponds
  *     to a system resume event. The 'time' field is for the time in
  *     milliseconds since the epoch when the system resumed. The 'sleepDuration'
  *     field is for the time in milliseconds the system spent in sleep/suspend
  *     state.
  */
 function showBatteryChargeData(powerSupplyArray, systemResumedArray) {
   var chargeTimeData = [];
+  var chargeAbsTime = [];
   var chargePlot = [
     {
+      name: loadTimeData.getString('batteryChargePercentageHeader'),
       color: '#0000FF',
       data: []
     }
   ];
   var dischargeRateTimeData = [];
+  var dischargeRateAbsTime = [];
   var dischargeRatePlot = [
     {
+      name: loadTimeData.getString('dischargeRateLegendText'),
       color: '#FF0000',
       data: []
     }
   ];
   var minDischargeRate = 1000;  // A high unrealistic number to begin with.
   var maxDischargeRate = -1000; // A low unrealistic number to begin with.
   for (var i = 0; i < powerSupplyArray.length; i++) {
     var j = Math.max(i - 1, 0);
 
-    addTimeDataSample(chargePlot, chargeTimeData,
+    addTimeDataSample(chargePlot,
+                      chargeTimeData,
+                      chargeAbsTime,
                       [powerSupplyArray[i].batteryPercent],
                       powerSupplyArray[i].time,
                       powerSupplyArray[j].time,
                       systemResumedArray);
 
     var dischargeRate = powerSupplyArray[i].batteryDischargeRate;
     minDischargeRate = Math.min(dischargeRate, minDischargeRate);
     maxDischargeRate = Math.max(dischargeRate, maxDischargeRate);
     addTimeDataSample(dischargeRatePlot,
                       dischargeRateTimeData,
+                      dischargeRateAbsTime,
                       [dischargeRate],
                       powerSupplyArray[i].time,
                       powerSupplyArray[j].time,
                       systemResumedArray);
   }
   if (minDischargeRate == maxDischargeRate) {
     // This means that all the samples had the same value. Hence, offset the
     // extremes by a bit so that the plot looks good.
     minDischargeRate -= 1;
     maxDischargeRate += 1;
   }
 
-  var chargeCanvas = $('battery-charge-percentage-canvas');
-  var dischargeRateCanvas = $('battery-discharge-rate-canvas');
-  plotLineGraph(chargeCanvas, chargeTimeData, chargePlot, 0.00, 100.00, 3);
-  plotLineGraph(dischargeRateCanvas,
-                dischargeRateTimeData,
-                dischargeRatePlot,
-                minDischargeRate,
-                maxDischargeRate,
-                3);
+  plotsDiv = $('battery-charge-plots-div');
+
+  canvases = addCanvases(
+      [loadTimeData.getString('batteryChargePercentageHeader'),
+       loadTimeData.getString('batteryDischargeRateHeader')],
+      plotsDiv);
+
+  batteryChargeCanvases = canvases[
+      loadTimeData.getString('batteryChargePercentageHeader')];
+  plotLineGraph(
+      batteryChargeCanvases['plot'],
+      batteryChargeCanvases['legend'],
+      chargeTimeData,
+      chargePlot,
+      0.00,
+      100.00,
+      3);
+
+  dischargeRateCanvases = canvases[
+      loadTimeData.getString('batteryDischargeRateHeader')];
+  plotLineGraph(
+      dischargeRateCanvases['plot'],
+      dischargeRateCanvases['legend'],
+      dischargeRateTimeData,
+      dischargeRatePlot,
+      minDischargeRate,
+      maxDischargeRate,
+      3);
+}
+
+/**
+ * Shows state occupancy data (CPU idle or CPU freq state occupancy) on a set of
+ * plots on the about:power UI.
+ *
+ * @param {Array.<{Array.<{
+ *     time: number,
+ *     cpuOnline:boolean,
+ *     timeInState: {<string>: number}>}>} timeInStateData Array of arrays
+ *     where each array corresponds to a CPU on the system. The elements of the
+ *     individual arrays contain state occupancy samples.
+ * @param {Array.<{time: ?, sleepDuration: ?}>} systemResumedArray An array
+ *     objects with fields 'time' and 'sleepDuration'. Each object corresponds
+ *     to a system resume event. The 'time' field is for the time in
+ *     milliseconds since the epoch when the system resumed. The 'sleepDuration'
+ *     field is for the time in milliseconds the system spent in sleep/suspend
+ *     state.
+ * @param {string} i18nHeaderString The header string to be displayed with each
+ *     plot. For example, CPU idle data will have its own header format, and CPU
+ *     freq data will have its header format.
+ * @param {string} unitString This is the string capturing the unit, if any,
+ *     for the different states. Note that this is not the unit of the data
+ *     being plotted.
+ * @param {HTMLDivElement} plotsDivId The div element in which the plots should
+ *     be added.
+ */
+function showStateOccupancyData(timeInStateData,
+                                systemResumedArray,
+                                i18nHeaderString,
+                                unitString,
+                                plotsDivId) {
+  var cpuPlots = [];
+  for (var cpu = 0; cpu < timeInStateData.length; cpu++) {
+    var cpuData = timeInStateData[cpu];
+    if (cpuData.length == 0) {
+      cpuPlots[cpu] = {plots: [], tData: []};
+      continue;
+    }
+    tData = [];
+    absTime = [];
+    // Each element of |plots| is an array of samples, one for each of the CPU
+    // states. The number of states is dicovered by looking at the first
+    // sample for which the CPU is online.
+    var plots = [];
+    var stateIndexMap = [];
+    var stateCount = 0;
+    for (var i = 0; i < cpuData.length; i++) {
+      if (cpuData[i].cpuOnline) {
+        for (var state in cpuData[i].timeInState) {
+          var stateName = state;
+          if (unitString != null) {
+            stateName += ' ' + unitString;
+          }
+          plots.push({
+              name: stateName,
+              data: [],
+              color: plotColors[stateCount]
+          });
+          stateIndexMap.push(state);
+          stateCount += 1;
+        }
+        break;
+      }
+    }
+    // If stateCount is 0, then it means the CPU has been offline
+    // throughout. Just add a single plot for such a case.
+    if (stateCount == 0) {
+      plots.push({
+          name: null,
+          data: [],
+          color: null
+      });
+      stateCount = 1; // Some invalid state!
+    }
+
+    // Pass the samples through the function addTimeDataSample to add 'sleep'
+    // samples.
+    for (var i = 0; i < cpuData.length; i++) {
+      var sample = cpuData[i];
+      var valArray = [];
+      for (var j = 0; j < stateCount; j++) {
+        if (sample.cpuOnline) {
+          valArray[j] = sample.timeInState[stateIndexMap[j]];
+        } else {
+          valArray[j] = offlineText;
+        }
+      }
+
+      var k = Math.max(i - 1, 0);
+      addTimeDataSample(plots,
+                        tData,
+                        absTime,
+                        valArray,
+                        sample.time,
+                        cpuData[k].time,
+                        systemResumedArray);
+    }
+
+    // Calculate the percentage occupancy of each state. A valid number is
+    // possible only if two consecutive samples are valid/numbers.
+    for (var k = 0; k < stateCount; k++) {
+      var stateData = plots[k].data;
+      // Skip the first sample as there is no previous sample.
+      for (var i = stateData.length - 1; i > 0; i--) {
+        if (typeof stateData[i] === 'number') {
+          if (typeof stateData[i - 1] === 'number') {
+            stateData[i] = (stateData[i] - stateData[i - 1]) /
+                           (absTime[i] - absTime[i - 1]) * 100;
+          } else {
+            stateData[i] = invalidDataText;
+          }
+        }
+      }
+    }
+
+    // Remove the first sample from the time and data arrays.
+    tData.shift();
+    for (var k = 0; k < stateCount; k++) {
+      plots[k].data.shift();
+    }
+    cpuPlots[cpu] = {plots: plots, tData: tData};
+  }
+
+  headers = [];
+  for (var cpu = 0; cpu < timeInStateData.length; cpu++) {
+    headers[cpu] =
+        'CPU ' + cpu + ' ' + loadTimeData.getString(i18nHeaderString);
+  }
+
+  canvases = addCanvases(headers, $(plotsDivId));
+  for (var cpu = 0; cpu < timeInStateData.length; cpu++) {
+    cpuCanvases = canvases[headers[cpu]];
+    plotLineGraph(cpuCanvases['plot'],
+                  cpuCanvases['legend'],
+                  cpuPlots[cpu]['tData'],
+                  cpuPlots[cpu]['plots'],
+                  0,
+                  100,
+                  3);
+  }
+}
+
+function showCpuIdleData(idleStateData, systemResumedArray) {
+  showStateOccupancyData(idleStateData,
+                         systemResumedArray,
+                         'idleStateOccupancyPercentageHeader',
+                         null,
+                         'cpu-idle-plots-div');
+}
+
+function showCpuFreqData(freqStateData, systemResumedArray) {
+  showStateOccupancyData(freqStateData,
+                         systemResumedArray,
+                         'frequencyStateOccupancyPercentageHeader',
+                         'MHz',
+                         'cpu-freq-plots-div');
 }
 
 function requestBatteryChargeData() {
   chrome.send('requestBatteryChargeData');
 }
 
+function requestCpuIdleData() {
+  chrome.send('requestCpuIdleData');
+}
+
+function requestCpuFreqData() {
+  chrome.send('requestCpuFreqData');
+}
+
+/**
+ * Return a callback for the 'Show'/'Hide' buttons for each section of the
+ * about:power page.
+ *
+ * @param {string} sectionId The ID of the section which is to be shown or
+ *     hidden.
+ * @param {string} buttonId The ID of the 'Show'/'Hide' button.
+ * @param {function} requestFunction The function which should be invoked on
+ *    'Show' to request for data from chrome.
+ * @return {function} The button callback function.
+ */
+function showHideCallback(sectionId, buttonId, requestFunction) {
+  return function() {
+    if ($(sectionId).hidden) {
+      $(sectionId).hidden = false;
+      $(buttonId).textContent = loadTimeData.getString('hideButton');
+      requestFunction();
+    } else {
+      $(sectionId).hidden = true;
+      $(buttonId).textContent = loadTimeData.getString('showButton');
+    }
+  }
+}
+
 var powerUI = {
-  showBatteryChargeData: showBatteryChargeData
+  showBatteryChargeData: showBatteryChargeData,
+  showCpuIdleData: showCpuIdleData,
+  showCpuFreqData: showCpuFreqData
 };
 
 document.addEventListener('DOMContentLoaded', function() {
-  requestBatteryChargeData();
+  $('battery-charge-section').hidden = true;
+  $('battery-charge-show-button').onclick = showHideCallback(
+      'battery-charge-section',
+      'battery-charge-show-button',
+      requestBatteryChargeData);
   $('battery-charge-reload-button').onclick = requestBatteryChargeData;
+
+  $('cpu-idle-section').hidden = true;
+  $('cpu-idle-show-button').onclick = showHideCallback(
+      'cpu-idle-section', 'cpu-idle-show-button', requestCpuIdleData);
+  $('cpu-idle-reload-button').onclick = requestCpuIdleData;
+

[arv (Not doing code reviews), 2014/03/10 17:00:46]

remove empty line

[Siva Chandra, 2014/03/10 18:46:09]

Done.

+
+  $('cpu-freq-section').hidden = true;
+  $('cpu-freq-show-button').onclick = showHideCallback(
+      'cpu-freq-section', 'cpu-freq-show-button', requestCpuFreqData);
+  $('cpu-freq-reload-button').onclick = requestCpuFreqData;
 });