Add a percentage to each metric in the V8 timeline plot

tools/plot-timer-events.js

Index: tools/plot-timer-events.js
diff --git a/tools/plot-timer-events.js b/tools/plot-timer-events.js
index 0a5e5221ae210523f8de835265aad981b1bd1786..00e40f8cfe42ce5222702701c0a210632fe5a6ef 100644
--- a/tools/plot-timer-events.js
+++ b/tools/plot-timer-events.js
@@ -500,11 +500,26 @@ function GnuplotOutput() {
   print("set xtics out nomirror");
   print("unset key");
 
+  var percentages = {};
+  var total = 0;
+  for (var name in TimerEvents) {
+    var event = TimerEvents[name];
+    var ranges = MergeRanges(event.ranges);
+    var exclude_ranges = [new Range(-Infinity, xrange_start),
+                          new Range(xrange_end, Infinity)];
+    ranges = ExcludeRanges(ranges, exclude_ranges);
+    var sum = 0;
+    for (var i = 0; i < ranges.length; i++) {
+      sum += ranges[i].end - ranges[i].start;
+    }
+    percentages[name] = (sum / (xrange_end - xrange_start) * 100).toFixed(1);
+  }
+
   // Name Y-axis.
   var ytics = [];
   for (name in TimerEvents) {
     var index = TimerEvents[name].index;
-    ytics.push('"' + name + '"' + ' ' + index);
+    ytics.push('"' + name + ' (' + percentages[name] + '%%)" ' + index);
   }
   ytics.push('"code kind being executed"' + ' ' + (kY1Offset - 1));
   ytics.push('"top ' + kStackFrames + ' js stack frames"' + ' ' +