Don't shrink starting_rect in the first round.

cc/resources/picture_layer_tiling_unittest.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/resources/picture_layer_tiling.h"
 
 #include "cc/test/fake_picture_layer_tiling_client.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/size_conversions.h"
@@ skipping 420 matching lines @@
   gfx::Rect out = PictureLayerTiling::ExpandRectEquallyToAreaBoundedBy(
       in, target_area, bounds);
   EXPECT_EQ(bounds.right(), out.right());
   EXPECT_EQ(bounds.bottom(), out.bottom());
   EXPECT_LE(out.width() * out.height(), target_area);
   EXPECT_GT(out.width() * out.height(),
             target_area - out.width() - out.height());
   EXPECT_TRUE(bounds.Contains(out));
 }
 
+TEST(PictureLayerTilingTest, ShrinkRectContainingBounds) {
+  gfx::Rect in(0, 0, 600, 600);
+  gfx::Rect bounds(0, 0, 10, 10);
+  int64 target_area = 20 * 20;
+  gfx::Rect out = PictureLayerTiling::ExpandRectEquallyToAreaBoundedBy(
+      in, target_area, bounds);
+  EXPECT_EQ(bounds.ToString(), out.ToString());
+}
+
 TEST(PictureLayerTilingTest, EmptyStartingRect) {
   // If a layer has a non-invertible transform, then the starting rect
   // for the layer would be empty.
   gfx::Rect in(40, 40, 0, 0);
   gfx::Rect bounds(0, 0, 10, 10);
   int64 target_area = 400 * 400;
   gfx::Rect out = PictureLayerTiling::ExpandRectEquallyToAreaBoundedBy(
       in, target_area, bounds);
   EXPECT_TRUE(out.IsEmpty());
 }
@@ skipping 38 matching lines @@
       gfx::Transform(),  // current screen transform
       2,  // current frame number
       2.0,  // current frame time
       false,  // store screen space quads on tiles
       10000);  // max tiles in tile manager
   VerifyTiles(1.f, gfx::Rect(), base::Bind(&TileExists, false));
 }
 
 }  // namespace
 }  // namespace cc