[CSSMQ] Use initial values as base for relative units.

Source/core/css/MediaQueryEvaluator.cpp

 /*
  * CSS Media Query Evaluator
  *
  * Copyright (C) 2006 Kimmo Kinnunen <kimmo.t.kinnunen@nokia.com>.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ skipping 319 matching lines @@
 static bool gridMediaFeatureEval(CSSValue* value, RenderStyle*, Frame*, MediaFeaturePrefix op)
 {
     // if output device is bitmap, grid: 0 == true
     // assume we have bitmap device
     float number;
     if (value && numberValue(value, number))
         return compareValue(static_cast<int>(number), 0, op);
     return false;
 }
 
-static bool computeLength(CSSValue* value, bool strict, RenderStyle* style, RenderStyle* rootStyle, int& result)
+static bool computeLength(CSSValue* value, bool strict, RenderStyle* initialStyle, int& result)
 {
     if (!value->isPrimitiveValue())
         return false;
 
     CSSPrimitiveValue* primitiveValue = toCSSPrimitiveValue(value);
 
     if (primitiveValue->isNumber()) {
         result = primitiveValue->getIntValue();
         return !strict || !result;
     }
 
     if (primitiveValue->isLength()) {
-        result = primitiveValue->computeLength<int>(style, rootStyle, 1.0 /* multiplier */, true /* computingFontSize */);
+        // Relative (like EM) and root relative (like REM) units are always resolved against the initial values
+        // for media queries, hence the two initialStyle parameters.
+        result = primitiveValue->computeLength<int>(initialStyle, initialStyle, 1.0 /* multiplier */, true /* computingFontSize */);
         return true;
     }
 
     return false;
 }
 
 static bool deviceHeightMediaFeatureEval(CSSValue* value, RenderStyle* style, Frame* frame, MediaFeaturePrefix op)
 {
     if (value) {
         FloatRect sg = screenRect(frame->page()->mainFrame()->view());
-        RenderStyle* rootStyle = frame->document()->documentElement()->renderStyle();
         int length;
         long height = sg.height();
         InspectorInstrumentation::applyScreenHeightOverride(frame, &height);
-        return computeLength(value, !frame->document()->inQuirksMode(), style, rootStyle, length) && compareValue(static_cast<int>(height), length, op);
+        return computeLength(value, !frame->document()->inQuirksMode(), style, length) && compareValue(static_cast<int>(height), length, op);
     }
     // ({,min-,max-}device-height)
     // assume if we have a device, assume non-zero
     return true;
 }
 
 static bool deviceWidthMediaFeatureEval(CSSValue* value, RenderStyle* style, Frame* frame, MediaFeaturePrefix op)
 {
     if (value) {
         FloatRect sg = screenRect(frame->page()->mainFrame()->view());
-        RenderStyle* rootStyle = frame->document()->documentElement()->renderStyle();
         int length;
         long width = sg.width();
         InspectorInstrumentation::applyScreenWidthOverride(frame, &width);
-        return computeLength(value, !frame->document()->inQuirksMode(), style, rootStyle, length) && compareValue(static_cast<int>(width), length, op);
+        return computeLength(value, !frame->document()->inQuirksMode(), style, length) && compareValue(static_cast<int>(width), length, op);
     }
     // ({,min-,max-}device-width)
     // assume if we have a device, assume non-zero
     return true;
 }
 
 static bool heightMediaFeatureEval(CSSValue* value, RenderStyle* style, Frame* frame, MediaFeaturePrefix op)
 {
     FrameView* view = frame->view();
 
     int height = viewportSize(view).height();
     if (value) {
         if (RenderView* renderView = frame->document()->renderView())
             height = adjustForAbsoluteZoom(height, renderView);
-        RenderStyle* rootStyle = frame->document()->documentElement()->renderStyle();
         int length;
-        return computeLength(value, !frame->document()->inQuirksMode(), style, rootStyle, length) && compareValue(height, length, op);
+        return computeLength(value, !frame->document()->inQuirksMode(), style, length) && compareValue(height, length, op);
     }
 
     return height;
 }
 
 static bool widthMediaFeatureEval(CSSValue* value, RenderStyle* style, Frame* frame, MediaFeaturePrefix op)
 {
     FrameView* view = frame->view();
 
     int width = viewportSize(view).width();
     if (value) {
         if (RenderView* renderView = frame->document()->renderView())
             width = adjustForAbsoluteZoom(width, renderView);
-        RenderStyle* rootStyle = frame->document()->documentElement()->renderStyle();
         int length;
-        return computeLength(value, !frame->document()->inQuirksMode(), style, rootStyle, length) && compareValue(width, length, op);
+        return computeLength(value, !frame->document()->inQuirksMode(), style, length) && compareValue(width, length, op);
     }
 
     return width;
 }
 
 // rest of the functions are trampolines which set the prefix according to the media feature expression used
 
 static bool minColorMediaFeatureEval(CSSValue* value, RenderStyle* style, Frame* frame, MediaFeaturePrefix)
 {
     return colorMediaFeatureEval(value, style, frame, MinPrefix);
@@ skipping 261 matching lines @@
     // and let trampoline functions override the prefix if prefix is
     // used
     EvalFunc func = gFunctionMap->get(expr->mediaFeature().impl());
     if (func)
         return func(expr->value(), m_style.get(), m_frame, NoPrefix);
 
     return false;
 }
 
 } // namespace