Revert of cc: Stop locking the raster scale factor at 1 after any change.

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 0849c516bab58e63b183c957eb877e748f85187a..732b822aa8b78486622b95429e3d29e35c7b14cd 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -69,6 +69,7 @@
       raster_source_scale_(0.f),
       raster_contents_scale_(0.f),
       low_res_raster_contents_scale_(0.f),
+      raster_source_scale_is_fixed_(false),
       was_screen_space_transform_animating_(false),
       only_used_low_res_last_append_quads_(false),
       is_mask_(is_mask),
@@ -889,8 +890,10 @@
   if (raster_device_scale_ != ideal_device_scale_)
     return true;
 
-  // When the source scale changes we want to match it, but not when animating.
+  // When the source scale changes we want to match it, but not when animating
+  // or when we've fixed the scale in place.
   if (!draw_properties().screen_space_transform_is_animating &&
+      !raster_source_scale_is_fixed_ &&
       raster_source_scale_ != ideal_source_scale_)
     return true;
 
@@ -931,13 +934,32 @@
 }
 
 void PictureLayerImpl::RecalculateRasterScales() {
-  const float old_raster_contents_scale = raster_contents_scale_;
-  const float old_raster_page_scale = raster_page_scale_;
+  float old_raster_contents_scale = raster_contents_scale_;
+  float old_raster_page_scale = raster_page_scale_;
+  float old_raster_source_scale = raster_source_scale_;
 
   raster_device_scale_ = ideal_device_scale_;
   raster_page_scale_ = ideal_page_scale_;
   raster_source_scale_ = ideal_source_scale_;
   raster_contents_scale_ = ideal_contents_scale_;
+
+  // If we're not animating, or leaving an animation, and the
+  // ideal_source_scale_ changes, then things are unpredictable, and we fix
+  // the raster_source_scale_ in place.
+  if (old_raster_source_scale &&
+      !draw_properties().screen_space_transform_is_animating &&
+      !was_screen_space_transform_animating_ &&
+      old_raster_source_scale != ideal_source_scale_)
+    raster_source_scale_is_fixed_ = true;
+
+  // TODO(danakj): Adjust raster source scale closer to ideal source scale at
+  // a throttled rate. Possibly make use of invalidation_.IsEmpty() on pending
+  // tree. This will allow CSS scale changes to get re-rastered at an
+  // appropriate rate. (crbug.com/413636)
+  if (raster_source_scale_is_fixed_) {
+    raster_contents_scale_ /= raster_source_scale_;
+    raster_source_scale_ = 1.f;
+  }
 
   // During pinch we completely ignore the current ideal scale, and just use
   // a multiple of the previous scale.
@@ -1107,6 +1129,7 @@
   raster_source_scale_ = 0.f;
   raster_contents_scale_ = 0.f;
   low_res_raster_contents_scale_ = 0.f;
+  raster_source_scale_is_fixed_ = false;
 }
 
 bool PictureLayerImpl::CanHaveTilings() const {
@@ -1190,7 +1213,6 @@
     base::trace_event::TracedValue* state) const {
   LayerImpl::AsValueInto(state);
   state->SetDouble("ideal_contents_scale", ideal_contents_scale_);
-  state->SetDouble("raster_contents_scale", raster_contents_scale_);
   state->SetDouble("geometry_contents_scale", MaximumTilingContentsScale());
   state->BeginArray("tilings");
   tilings_->AsValueInto(state);