Force use of and cache render surface.

cc/trees/damage_tracker.cc

Index: cc/trees/damage_tracker.cc
diff --git a/cc/trees/damage_tracker.cc b/cc/trees/damage_tracker.cc
index 5dff7581824556b505863ed27ef94bdcee526699..aa738a389863b600ae7714dce41105a949c9d265 100644
--- a/cc/trees/damage_tracker.cc
+++ b/cc/trees/damage_tracker.cc
@@ -25,8 +25,7 @@ std::unique_ptr<DamageTracker> DamageTracker::Create() {
   return base::WrapUnique(new DamageTracker());
 }
 
-DamageTracker::DamageTracker()
-  : mailboxId_(0) {}
+DamageTracker::DamageTracker() : mailboxId_(0) {}
 
 DamageTracker::~DamageTracker() {}
 
@@ -364,7 +363,6 @@ void DamageTracker::AccumulateDamageFromLayer(LayerImpl* layer) {
   // its target RenderSurface, even if that layer owns the target RenderSurface
   // itself. To consider how a layer's target surface contributes to the
   // ancestor surface, ExtendDamageForRenderSurface() must be called instead.
-
   bool layer_is_new = false;
   LayerRectMapData& data = RectDataForLayer(layer->id(), &layer_is_new);
   gfx::Rect old_rect_in_target_space = data.rect_;
@@ -380,19 +378,21 @@ void DamageTracker::AccumulateDamageFromLayer(LayerImpl* layer) {
     // The layer's old region is now exposed on the target surface, too.
     // Note old_rect_in_target_space is already in target space.
     damage_for_this_update_.Union(old_rect_in_target_space);
-    return;
+  } else {
+    // If the layer properties haven't changed, then the the target surface is
+    // only affected by the layer's damaged area, which could be empty.
+    gfx::Rect damage_rect =
+        gfx::UnionRects(layer->update_rect(), layer->damage_rect());
+    damage_rect.Intersect(gfx::Rect(layer->bounds()));
+    if (!damage_rect.IsEmpty()) {
+      gfx::Rect damage_rect_in_target_space = MathUtil::MapEnclosingClippedRect(
+          layer->DrawTransform(), damage_rect);
+      damage_for_this_update_.Union(damage_rect_in_target_space);
+    }
   }
 
-  // If the layer properties haven't changed, then the the target surface is
-  // only affected by the layer's damaged area, which could be empty.
-  gfx::Rect damage_rect =
-      gfx::UnionRects(layer->update_rect(), layer->damage_rect());
-  damage_rect.Intersect(gfx::Rect(layer->bounds()));
-  if (!damage_rect.IsEmpty()) {
-    gfx::Rect damage_rect_in_target_space =
-        MathUtil::MapEnclosingClippedRect(layer->DrawTransform(), damage_rect);
-    damage_for_this_update_.Union(damage_rect_in_target_space);
-  }
+  if (layer_is_new || !layer->LayerPropertyChanged())

[wutao, 2017/06/09 19:19:10]

This might need special check:
If the layer is the target of itself, then we did not include this layer's
property change.
However, if the layer is subtree of the target surface, we should include the
layer's property change.

+    has_damage_from_contributing_content_ |= !damage_for_this_update_.IsEmpty();
 }
 
 void DamageTracker::AccumulateDamageFromRenderSurface(
@@ -456,6 +456,9 @@ void DamageTracker::AccumulateDamageFromRenderSurface(
     ExpandDamageInsideRectWithFilters(surface_rect_in_target_space,
                                       background_filters);
   }
+
+  if (surface_is_new || !render_surface->SurfacePropertyChanged())
+    has_damage_from_contributing_content_ |= !damage_for_this_update_.IsEmpty();
 }
 
 bool DamageTracker::DamageAccumulator::GetAsRect(gfx::Rect* rect) {