Don't use DF text during animations

Previously, we enabled distance-field text during animations in
order to improve GPU raster performance. Now that GPU raster
handles animations the same way as SW - only rastering at specific
scales and interpolating, this optimization isn't necessary.

In certain cases, the optimization causes visual differences
between non-animating and animating content, so removing this
improves our correctness as well.

R=ajuma@chromium.org
BUG=668723
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2605273003
Cr-Commit-Position: refs/heads/master@{#441204}

cc/layers/picture_layer_impl.cc

@@ -478,9 +478,6 @@ bool PictureLayerImpl::UpdateTiles() {
   was_screen_space_transform_animating_ =
       draw_properties().screen_space_transform_is_animating;
 
-  if (screen_space_transform_is_animating())
-    raster_source_->SetShouldAttemptToUseDistanceFieldText();
-
   double current_frame_time_in_seconds =
       (layer_tree_impl()->CurrentBeginFrameArgs().frame_time -
        base::TimeTicks()).InSecondsF();

cc/layers/picture_layer_impl_unittest.cc

@@ -2586,7 +2586,6 @@ TEST_F(PictureLayerImplTest, HighResTilingDuringAnimation) {
                                maximum_animation_scale,
                                starting_animation_scale, animating_transform);
   EXPECT_BOTH_EQ(HighResTiling()->contents_scale_key(), 3.f);
-  EXPECT_BOTH_TRUE(GetRasterSource()->ShouldAttemptToUseDistanceFieldText());
 
   // Further changes to scale during the animation should not cause a new
   // high-res tiling to get created.

cc/playback/raster_source.cc

@@ -40,7 +40,6 @@ RasterSource::RasterSource(const RecordingSource* other, bool can_use_lcd_text)
       clear_canvas_with_debug_color_(other->clear_canvas_with_debug_color_),
       slow_down_raster_scale_factor_for_debug_(
           other->slow_down_raster_scale_factor_for_debug_),
-      should_attempt_to_use_distance_field_text_(false),
       image_decode_cache_(nullptr) {}
 
 RasterSource::RasterSource(const RasterSource* other, bool can_use_lcd_text)
@@ -56,8 +55,6 @@ RasterSource::RasterSource(const RasterSource* other, bool can_use_lcd_text)
       clear_canvas_with_debug_color_(other->clear_canvas_with_debug_color_),
       slow_down_raster_scale_factor_for_debug_(
           other->slow_down_raster_scale_factor_for_debug_),
-      should_attempt_to_use_distance_field_text_(
-          other->should_attempt_to_use_distance_field_text_),
       image_decode_cache_(other->image_decode_cache_) {}
 
 RasterSource::~RasterSource() {
@@ -277,14 +274,6 @@ gfx::Rect RasterSource::RecordedViewport() const {
   return recorded_viewport_;
 }
 
-void RasterSource::SetShouldAttemptToUseDistanceFieldText() {
-  should_attempt_to_use_distance_field_text_ = true;
-}
-
-bool RasterSource::ShouldAttemptToUseDistanceFieldText() const {
-  return should_attempt_to_use_distance_field_text_;
-}
-
 void RasterSource::AsValueInto(base::trace_event::TracedValue* array) const {
   if (display_list_.get())
     TracedValue::AppendIDRef(display_list_.get(), array);

cc/playback/raster_source.h

@@ -107,14 +107,6 @@ class CC_EXPORT RasterSource : public base::RefCountedThreadSafe<RasterSource> {
   // Valid rectangle in which everything is recorded and can be rastered from.
   virtual gfx::Rect RecordedViewport() const;
 
-  // Informs the raster source that it should attempt to use distance field text
-  // during rasterization.
-  virtual void SetShouldAttemptToUseDistanceFieldText();
-
-  // Return true iff this raster source would benefit from using distance
-  // field text.
-  virtual bool ShouldAttemptToUseDistanceFieldText() const;
-
   // Tracing functionality.
   virtual void DidBeginTracing();
   virtual void AsValueInto(base::trace_event::TracedValue* array) const;
@@ -153,9 +145,6 @@ class CC_EXPORT RasterSource : public base::RefCountedThreadSafe<RasterSource> {
   const gfx::Size size_;
   const bool clear_canvas_with_debug_color_;
   const int slow_down_raster_scale_factor_for_debug_;
-  // TODO(enne/vmiura): this has a read/write race between raster and compositor
-  // threads with multi-threaded Ganesh.  Make this const or remove it.
-  bool should_attempt_to_use_distance_field_text_;
 
   // In practice, this is only set once before raster begins, so it's ok with
   // respect to threading.

cc/raster/gpu_raster_buffer_provider.cc

@@ -213,16 +213,11 @@ void GpuRasterBufferProvider::PlaybackOnWorkerThread(
     gl->WaitSyncTokenCHROMIUM(sync_token.GetConstData());
   }
 
-  // Turn on distance fields for layers that have ever animated.
-  bool use_distance_field_text =
-      use_distance_field_text_ ||
-      raster_source->ShouldAttemptToUseDistanceFieldText();
-
   RasterizeSource(raster_source, resource_has_previous_content,
                   resource_lock->size(), raster_full_rect, raster_dirty_rect,
                   scales, playback_settings, worker_context_provider_,
                   resource_lock, async_worker_context_enabled_,
-                  use_distance_field_text, msaa_sample_count_);
+                  use_distance_field_text_, msaa_sample_count_);
 
   const uint64_t fence_sync = gl->InsertFenceSyncCHROMIUM();