Fix scale on axis may be negative.

cc/base/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 "cc/base/math_util.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 
@@ skipping 468 matching lines @@
       scale_inner_rect.origin() - scale_outer_rect.origin();
   gfx::Vector2dF bottom_right_diff =
       scale_inner_rect.bottom_right() - scale_outer_rect.bottom_right();
   output_inner_rect.Inset(top_left_diff.x() / scale_rect_to_input_scale_x,
                           top_left_diff.y() / scale_rect_to_input_scale_y,
                           -bottom_right_diff.x() / scale_rect_to_input_scale_x,
                           -bottom_right_diff.y() / scale_rect_to_input_scale_y);
   return output_inner_rect;
 }
 
+static inline bool NearlyZero(double value) {
+  return std::abs(value) < std::numeric_limits<double>::epsilon();
+}
+
 static inline float ScaleOnAxis(double a, double b, double c) {
-  if (!b && !c)
-    return a;
-  if (!a && !c)
-    return b;
-  if (!a && !b)
-    return c;
+  if (NearlyZero(b) && NearlyZero(c))
+    return std::abs(a);
+  if (NearlyZero(a) && NearlyZero(c))
+    return std::abs(b);
+  if (NearlyZero(a) && NearlyZero(b))
+    return std::abs(c);
 
   // Do the sqrt as a double to not lose precision.
   return static_cast<float>(std::sqrt(a * a + b * b + c * c));
 }
 
 gfx::Vector2dF MathUtil::ComputeTransform2dScaleComponents(
     const gfx::Transform& transform,
     float fallback_value) {
   if (transform.HasPerspective())
     return gfx::Vector2dF(fallback_value, fallback_value);
@@ skipping 127 matching lines @@
   return scoped_ptr<base::Value>(base::Value::CreateDoubleValue(
       std::min(value, std::numeric_limits<double>::max())));
 }
 
 scoped_ptr<base::Value> MathUtil::AsValueSafely(float value) {
   return scoped_ptr<base::Value>(base::Value::CreateDoubleValue(
       std::min(value, std::numeric_limits<float>::max())));
 }
 
 }  // namespace cc