cc: Add some early outs to avoid expensive operations

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 "cc/math_util.h"
 
 #include <cmath>
 #include <limits>
@@ skipping 99 matching lines @@
 
 gfx::RectF MathUtil::mapClippedRect(const WebTransformationMatrix& transform, const gfx::RectF& srcRect)
 {
     if (transform.isIdentityOrTranslation()) {
         gfx::RectF mappedRect(srcRect);
         mappedRect.Offset(static_cast<float>(transform.m41()), static_cast<float>(transform.m42()));
         return mappedRect;
     }
 
     // Apply the transform, but retain the result in homogeneous coordinates.
-    gfx::QuadF q = gfx::QuadF(gfx::RectF(srcRect));
+    gfx::QuadF q = gfx::QuadF(srcRect);
     HomogeneousCoordinate h1 = mapHomogeneousPoint(transform, gfx::Point3F(q.p1()));
     HomogeneousCoordinate h2 = mapHomogeneousPoint(transform, gfx::Point3F(q.p2()));
     HomogeneousCoordinate h3 = mapHomogeneousPoint(transform, gfx::Point3F(q.p3()));
     HomogeneousCoordinate h4 = mapHomogeneousPoint(transform, gfx::Point3F(q.p4()));
 
     return computeEnclosingClippedRect(h1, h2, h3, h4);
 }
 
 gfx::RectF MathUtil::projectClippedRect(const WebTransformationMatrix& transform, const gfx::RectF& srcRect)
 {
+    if (transform.isIdentityOrTranslation()) {
+        gfx::RectF projectedRect(srcRect);
+        projectedRect.Offset(static_cast<float>(transform.m41()), static_cast<float>(transform.m42()));
+        return projectedRect;
+    }
+
     // Perform the projection, but retain the result in homogeneous coordinates.
-    gfx::QuadF q = gfx::QuadF(gfx::RectF(srcRect));
+    gfx::QuadF q = gfx::QuadF(srcRect);
     HomogeneousCoordinate h1 = projectHomogeneousPoint(transform, q.p1());
     HomogeneousCoordinate h2 = projectHomogeneousPoint(transform, q.p2());
     HomogeneousCoordinate h3 = projectHomogeneousPoint(transform, q.p3());
     HomogeneousCoordinate h4 = projectHomogeneousPoint(transform, q.p4());
 
     return computeEnclosingClippedRect(h1, h2, h3, h4);
 }
 
 void MathUtil::mapClippedQuad(const WebTransformationMatrix& transform, const gfx::QuadF& srcQuad, gfx::PointF clippedQuad[8], int& numVerticesInClippedQuad)
 {
@@ skipping 248 matching lines @@
     return static_cast<float>(Rad2Deg(std::acos(dotProduct)));
 }
 
 gfx::Vector2dF MathUtil::projectVector(gfx::Vector2dF source, gfx::Vector2dF destination)
 {
     float projectedLength = gfx::DotProduct(source, destination) / destination.LengthSquared();
     return gfx::Vector2dF(projectedLength * destination.x(), projectedLength * destination.y());
 }
 
 }  // namespace cc