cc: Apply the layer's initial CSS scale to the contentsScale to render text at the right resolution.

cc/math_util.cc

 // Copyright 2012 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.
 
 #include "config.h"
 
 #include "CCMathUtil.h"
 
 #include "FloatPoint.h"
 #include "FloatQuad.h"
 #include "IntRect.h"
+#include <cmath>
 #include <public/WebTransformationMatrix.h>
 
 using WebKit::WebTransformationMatrix;
 
 namespace cc {
 
 static HomogeneousCoordinate projectHomogeneousPoint(const WebTransformationMatrix& transform, const FloatPoint& p)
 {
     // In this case, the layer we are trying to project onto is perpendicular to ray
     // (point p and z-axis direction) that we are trying to project. This happens when the
@@ skipping 332 matching lines @@
     //
     transform.setM13(0);
     transform.setM23(0);
     transform.setM31(0);
     transform.setM32(0);
     transform.setM33(1);
     transform.setM34(0);
     transform.setM43(0);
 }
 
+static inline float scaleOnAxis(double a, double b, double c)
+{
+    return std::sqrt(a * a + b * b + c * c);
+}
+
+FloatPoint CCMathUtil::computeTransform2dScaleComponents(const WebTransformationMatrix& transform)
+{
+    if (transform.hasPerspective())
+        return FloatPoint(1, 1);
+    float xScale = scaleOnAxis(transform.m11(), transform.m12(), transform.m13());
+    float yScale = scaleOnAxis(transform.m21(), transform.m22(), transform.m23());
+    return FloatPoint(xScale, yScale);
+}
+
 float CCMathUtil::smallestAngleBetweenVectors(const FloatSize& v1, const FloatSize& v2)
 {
     float dotProduct = (v1.width() * v2.width() + v1.height() * v2.height()) / (v1.diagonalLength() * v2.diagonalLength());
     // Clamp to compensate for rounding errors.
     dotProduct = std::max(-1.f, std::min(1.f, dotProduct));
     return rad2deg(acosf(dotProduct));
 }
 
 FloatSize CCMathUtil::projectVector(const FloatSize& source, const FloatSize& destination)
 {
     float sourceDotDestination = source.width() * destination.width() + source.height() * destination.height();
     float projectedLength = sourceDotDestination / destination.diagonalLengthSquared();
     return FloatSize(projectedLength * destination.width(), projectedLength * destination.height());
 }
 
 } // namespace cc