cc: Make PictureLayerImpl use a better choice for animated raster scale.

cc/layers/picture_layer_impl_unittest.cc

 // Copyright 2013 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/layers/picture_layer_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 #include <utility>
@@ skipping 1077 matching lines @@
                                page_scale,
                                maximum_animation_scale,
                                animating_transform);
   EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), 1.f);
   EXPECT_BOTH_EQ(LowResTiling()->contents_scale(), low_res_factor);
   EXPECT_BOTH_EQ(num_tilings(), 2u);
 
   // Page scale animation, new high res, but not new low res because animating.
   contents_scale = 2.f;
   page_scale = 2.f;
+  maximum_animation_scale = 2.f;
   animating_transform = true;
   SetContentsScaleOnBothLayers(contents_scale,
                                device_scale,
                                page_scale,
                                maximum_animation_scale,
                                animating_transform);
   EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), 2.f);
   EXPECT_BOTH_EQ(LowResTiling()->contents_scale(), low_res_factor);
   EXPECT_BOTH_EQ(num_tilings(), 3u);
 
@@ skipping 1200 matching lines @@
   animating_transform = false;
 
   SetContentsScaleOnBothLayers(contents_scale,
                                device_scale,
                                page_scale,
                                maximum_animation_scale,
                                animating_transform);
   EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), 4.f);
 
   // When animating with an unknown maximum animation scale factor, a new
-  // high-res tiling should be created at the animation's initial scale.
+  // high-res tiling should be created at a source scale of 1.
   animating_transform = true;
   contents_scale = 2.f;
   maximum_animation_scale = 0.f;
 
   SetContentsScaleOnBothLayers(contents_scale,
                                device_scale,
                                page_scale,
                                maximum_animation_scale,
                                animating_transform);
-  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), 2.f);
+  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), page_scale * device_scale);
 
   // Further changes to scale during the animation should not cause a new
   // high-res tiling to get created.
   contents_scale = 3.f;
 
   SetContentsScaleOnBothLayers(contents_scale,
                                device_scale,
                                page_scale,
                                maximum_animation_scale,
                                animating_transform);
-  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), 2.f);
+  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), page_scale * device_scale);
 
   // Once we stop animating, a new high-res tiling should be created.
   animating_transform = false;
   contents_scale = 4.f;
 
   SetContentsScaleOnBothLayers(contents_scale,
                                device_scale,
                                page_scale,
                                maximum_animation_scale,
                                animating_transform);
   EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), 4.f);
 
   // When animating with a maxmium animation scale factor that is so large
   // that the layer grows larger than the viewport at this scale, a new
-  // high-res tiling should get created at the animation's initial scale, not
-  // at its maximum scale.
+  // high-res tiling should get created at a source scale of 1, not at its
+  // maximum scale.
   animating_transform = true;
   contents_scale = 2.f;
   maximum_animation_scale = 11.f;
 
   SetContentsScaleOnBothLayers(contents_scale,
                                device_scale,
                                page_scale,
                                maximum_animation_scale,
                                animating_transform);
-  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), 2.f);
+  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), page_scale * device_scale);
 
   // Once we stop animating, a new high-res tiling should be created.
   animating_transform = false;
   contents_scale = 11.f;
 
   SetContentsScaleOnBothLayers(contents_scale,
                                device_scale,
                                page_scale,
                                maximum_animation_scale,
                                animating_transform);
   EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), 11.f);
 
   // When animating with a maxmium animation scale factor that is so large
   // that the layer grows larger than the viewport at this scale, and where
   // the intial source scale is < 1, a new high-res tiling should get created
   // at source scale 1.
   animating_transform = true;
   contents_scale = 0.1f;
   maximum_animation_scale = 11.f;
 
   SetContentsScaleOnBothLayers(contents_scale,
                                device_scale,
                                page_scale,
                                maximum_animation_scale,
                                animating_transform);
   EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), device_scale * page_scale);
 
   // Once we stop animating, a new high-res tiling should be created.
   animating_transform = false;
+  contents_scale = 12.f;
+
+  SetContentsScaleOnBothLayers(contents_scale,
+                               device_scale,
+                               page_scale,
+                               maximum_animation_scale,
+                               animating_transform);
+  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), 12.f);
+
+  // When animating toward a smaller scale, but that is still so large that the
+  // layer grows larger than the viewport at this scale, a new high-res tiling
+  // should get created at source scale 1.
+  animating_transform = true;
+  contents_scale = 11.f;
+  maximum_animation_scale = 11.f;
+
+  SetContentsScaleOnBothLayers(contents_scale,
+                               device_scale,
+                               page_scale,
+                               maximum_animation_scale,
+                               animating_transform);
+  EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), device_scale * page_scale);
+
+  // Once we stop animating, a new high-res tiling should be created.
+  animating_transform = false;
   contents_scale = 11.f;
 
   SetContentsScaleOnBothLayers(contents_scale,
                                device_scale,
                                page_scale,
                                maximum_animation_scale,
                                animating_transform);
   EXPECT_BOTH_EQ(HighResTiling()->contents_scale(), 11.f);
 }
 
@@ skipping 1965 matching lines @@
   SetupPendingTree(pending_pile2);
   ActivateTree();
 
   // We've switched to a solid color, so we should end up with no tilings.
   ASSERT_TRUE(active_layer_->tilings());
   EXPECT_EQ(0u, active_layer_->tilings()->num_tilings());
 }
 
 }  // namespace
 }  // namespace cc