cc cleanup: simplify mask_uv_scale and MaskUVRect().

cc/output/renderer_pixeltest.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 <stddef.h>
 #include <stdint.h>
 
 #include "base/message_loop/message_loop.h"
 #include "cc/output/gl_renderer.h"
 #include "cc/quads/draw_quad.h"
@@ skipping 1687 matching lines @@
   // the size of the child render pass.
   gfx::Rect sub_rect = gfx::Rect(50, 50, 200, 100);
   EXPECT_NE(sub_rect.x(), child_pass->output_rect.x());
   EXPECT_NE(sub_rect.y(), child_pass->output_rect.y());
   EXPECT_NE(sub_rect.right(), child_pass->output_rect.right());
   EXPECT_NE(sub_rect.bottom(), child_pass->output_rect.bottom());
 
   // Set up a mask on the RenderPassDrawQuad.
   RenderPassDrawQuad* mask_quad =
       root_pass->CreateAndAppendDrawQuad<RenderPassDrawQuad>();
-  mask_quad->SetNew(root_pass_shared_state,
-                    sub_rect,
-                    sub_rect,
-                    child_pass_id,
+  mask_quad->SetNew(root_pass_shared_state, sub_rect, sub_rect, child_pass_id,
                     mask_resource_id,
-                    gfx::Vector2dF(2.f, 1.f),     // mask_uv_scale
+                    gfx::Vector2dF(2.f / mask_rect.width(),
+                                   2.f / mask_rect.height()),  // mask_uv_scale
                     gfx::Size(mask_rect.size()),  // mask_texture_size
                     FilterOperations(),           // foreground filters
                     gfx::Vector2dF(),             // filters scale
                     FilterOperations());          // background filters
 
   // White background behind the masked render pass.
   SolidColorDrawQuad* white =
       root_pass->CreateAndAppendDrawQuad<SolidColorDrawQuad>();
   white->SetNew(root_pass_shared_state,
                 viewport_rect,
@@ skipping 1251 matching lines @@
 
   EXPECT_TRUE(this->RunPixelTest(
       &pass_list, base::FilePath(FILE_PATH_LITERAL("spiral.png")),
       FuzzyPixelOffByOneComparator(true)));
 }
 
 #endif  // !defined(OS_ANDROID)
 
 }  // namespace
 }  // namespace cc