Reland "Simplify how the FSLP background rect is chosen."

This is a reland of 94b94d9e

Original change's description:
> Simplify how the FSLP background rect is chosen.
> 
> Before, the background size was reconstituted from the layer tree by
> taking the union of of black and video layers. Now, the actual size is
> plumbed through.
> 
> Change-Id: I0cb643b350ef7e4fca06e3bfd419e24861a2e3c6
> Reviewed-on: https://chromium-review.googlesource.com/1142962
> Reviewed-by: ccameron <ccameron@chromium.org>
> Commit-Queue: Sidney San Martín <sdy@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#576521}

Change-Id: Idf5199a2aeb8be08b34e0594142c33b3ebed5b78
Reviewed-on: https://chromium-review.googlesource.com/1143960Reviewed-by: ccameron <ccameron@chromium.org>
Commit-Queue: Sidney San Martín <sdy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577590}

ui/accelerated_widget_mac/ca_layer_tree_coordinator.mm

@@ -48,7 +48,7 @@ void CALayerTreeCoordinator::CommitPendingTreesToCA(
   if (pending_ca_renderer_layer_tree_) {
     pending_ca_renderer_layer_tree_->CommitScheduledCALayers(
         root_ca_layer_.get(), std::move(current_ca_renderer_layer_tree_),
-        scale_factor_);
+        pixel_size_, scale_factor_);
     current_ca_renderer_layer_tree_.swap(pending_ca_renderer_layer_tree_);
   } else {
     TRACE_EVENT0("gpu", "Blank frame: No overlays or CALayers");

ui/accelerated_widget_mac/ca_layer_tree_unittest_mac.mm

@@ -80,7 +80,8 @@ void UpdateCALayerTree(std::unique_ptr<ui::CARendererLayerTree>& ca_layer_tree,
   bool result = ScheduleCALayer(new_ca_layer_tree.get(), properties);
   EXPECT_TRUE(result);
   new_ca_layer_tree->CommitScheduledCALayers(
-      superlayer, std::move(ca_layer_tree), properties->scale_factor);
+      superlayer, std::move(ca_layer_tree), properties->rect.size(),
+      properties->scale_factor);
   std::swap(new_ca_layer_tree, ca_layer_tree);
 }
 
@@ -508,8 +509,8 @@ TEST_F(CALayerTreeTest, SplitSortingContextZero) {
     bool result = ScheduleCALayer(ca_layer_tree.get(), &properties);
     EXPECT_TRUE(result);
   }
-  ca_layer_tree->CommitScheduledCALayers(superlayer_, nullptr,
-                                         properties.scale_factor);
+  ca_layer_tree->CommitScheduledCALayers(
+      superlayer_, nullptr, properties.rect.size(), properties.scale_factor);
 
   // Validate the root layer.
   EXPECT_EQ(1u, [[superlayer_ sublayers] count]);
@@ -588,8 +589,8 @@ TEST_F(CALayerTreeTest, SortingContexts) {
     bool result = ScheduleCALayer(ca_layer_tree.get(), &properties);
     EXPECT_TRUE(result);
   }
-  ca_layer_tree->CommitScheduledCALayers(superlayer_, nullptr,
-                                         properties.scale_factor);
+  ca_layer_tree->CommitScheduledCALayers(
+      superlayer_, nullptr, properties.rect.size(), properties.scale_factor);
 
   // Validate the root layer.
   EXPECT_EQ(1u, [[superlayer_ sublayers] count]);
@@ -882,7 +883,8 @@ TEST_F(CALayerTreeTest, FullscreenLowPower) {
     bool result = ScheduleCALayer(new_ca_layer_tree.get(), &properties);
     EXPECT_TRUE(result);
     new_ca_layer_tree->CommitScheduledCALayers(
-        superlayer_, std::move(ca_layer_tree), properties.scale_factor);
+        superlayer_, std::move(ca_layer_tree), properties.rect.size(),
+        properties.scale_factor);
     std::swap(new_ca_layer_tree, ca_layer_tree);
 
     // Validate the tree structure.
@@ -896,7 +898,7 @@ TEST_F(CALayerTreeTest, FullscreenLowPower) {
     EXPECT_EQ(1u, [[transform_layer sublayers] count]);
 
     // Validate the content layer and fullscreen low power mode.
-    EXPECT_TRUE(CGRectEqualToRect([root_layer frame], CGRectZero));
+    EXPECT_FALSE(CGRectEqualToRect([root_layer frame], CGRectZero));
     EXPECT_NE([root_layer backgroundColor], nil);
   }
 
@@ -909,7 +911,8 @@ TEST_F(CALayerTreeTest, FullscreenLowPower) {
     result = ScheduleCALayer(new_ca_layer_tree.get(), &properties);
     EXPECT_TRUE(result);
     new_ca_layer_tree->CommitScheduledCALayers(
-        superlayer_, std::move(ca_layer_tree), properties.scale_factor);
+        superlayer_, std::move(ca_layer_tree), properties.rect.size(),
+        properties.scale_factor);
     std::swap(new_ca_layer_tree, ca_layer_tree);
 
     // Validate the tree structure.
@@ -936,7 +939,8 @@ TEST_F(CALayerTreeTest, FullscreenLowPower) {
     result = ScheduleCALayer(new_ca_layer_tree.get(), &properties);
     EXPECT_TRUE(result);
     new_ca_layer_tree->CommitScheduledCALayers(
-        superlayer_, std::move(ca_layer_tree), properties.scale_factor);
+        superlayer_, std::move(ca_layer_tree), properties.rect.size(),
+        properties.scale_factor);
     std::swap(new_ca_layer_tree, ca_layer_tree);
 
     // Validate the tree structure.
@@ -963,7 +967,8 @@ TEST_F(CALayerTreeTest, FullscreenLowPower) {
     result = ScheduleCALayer(new_ca_layer_tree.get(), &properties_black);
     EXPECT_TRUE(result);
     new_ca_layer_tree->CommitScheduledCALayers(
-        superlayer_, std::move(ca_layer_tree), properties.scale_factor);
+        superlayer_, std::move(ca_layer_tree), properties.rect.size(),
+        properties.scale_factor);
     std::swap(new_ca_layer_tree, ca_layer_tree);
 
     // Validate the tree structure.

ui/accelerated_widget_mac/ca_renderer_layer_tree.h

@@ -51,6 +51,7 @@ class ACCELERATED_WIDGET_MAC_EXPORT CARendererLayerTree {
   // not re-used by |this| will be removed from the CALayer hierarchy.
   void CommitScheduledCALayers(CALayer* superlayer,
                                std::unique_ptr<CARendererLayerTree> old_tree,
+                               const gfx::Size& pixel_size,
                                float scale_factor);
 
   // Returns the contents used for a given solid color.
@@ -86,15 +87,12 @@ class ACCELERATED_WIDGET_MAC_EXPORT CARendererLayerTree {
     // to nil, so that its destructor will not remove an active CALayer.
     void CommitToCA(CALayer* superlayer,
                     RootLayer* old_layer,
+                    const gfx::Size& pixel_size,
                     float scale_factor);
 
-    // Check to see if the CALayer tree is just a video layer on a black
-    // background. If so, return true and set background_rect to the
-    // background's bounding rect, otherwise return false. CommitToCA() calls
-    // this function and, based on its return value, either gives the root
-    // layer this frame and a black background color or clears them.
-    bool WantsFullcreenLowPowerBackdrop(float scale_factor,
-                                        gfx::RectF* background_rect);
+    // Return true if the CALayer tree is just a video layer on a black or
+    // transparent background, false otherwise.
+    bool WantsFullcreenLowPowerBackdrop();
 
     std::vector<ClipAndSortingLayer> clip_and_sorting_layers;
     base::scoped_nsobject<CALayer> ca_layer;

ui/accelerated_widget_mac/ca_renderer_layer_tree.mm

@@ -220,6 +220,7 @@ bool CARendererLayerTree::ScheduleCALayer(const CARendererLayerParams& params) {
 void CARendererLayerTree::CommitScheduledCALayers(
     CALayer* superlayer,
     std::unique_ptr<CARendererLayerTree> old_tree,
+    const gfx::Size& pixel_size,
     float scale_factor) {
   TRACE_EVENT0("gpu", "CARendererLayerTree::CommitScheduledCALayers");
   RootLayer* old_root_layer = nullptr;
@@ -229,7 +230,7 @@ void CARendererLayerTree::CommitScheduledCALayers(
       old_root_layer = &old_tree->root_layer_;
   }
 
-  root_layer_.CommitToCA(superlayer, old_root_layer, scale_factor);
+  root_layer_.CommitToCA(superlayer, old_root_layer, pixel_size, scale_factor);
   // If there are any extra CALayers in |old_tree| that were not stolen by this
   // tree, they will be removed from the CALayer tree in this deallocation.
   old_tree.reset();
@@ -237,9 +238,7 @@ void CARendererLayerTree::CommitScheduledCALayers(
   scale_factor_ = scale_factor;
 }
 
-bool CARendererLayerTree::RootLayer::WantsFullcreenLowPowerBackdrop(
-    float scale_factor,
-    gfx::RectF* background_rect) {
+bool CARendererLayerTree::RootLayer::WantsFullcreenLowPowerBackdrop() {
   bool found_video_layer = false;
   for (auto& clip_layer : clip_and_sorting_layers) {
     for (auto& transform_layer : clip_layer.transform_layers) {
@@ -250,7 +249,6 @@ bool CARendererLayerTree::RootLayer::WantsFullcreenLowPowerBackdrop(
 
         // See if this is the video layer.
         if (content_layer.use_av_layer) {
-          background_rect->Union(gfx::RectF(content_layer.rect));
           found_video_layer = true;
           if (!transform_layer.transform.IsPositiveScaleOrTranslation())
             return false;
@@ -263,15 +261,13 @@ bool CARendererLayerTree::RootLayer::WantsFullcreenLowPowerBackdrop(
         // solid black or transparent
         if (content_layer.io_surface)
           return false;
-        if (content_layer.background_color == SK_ColorBLACK) {
-          background_rect->Union(gfx::RectF(content_layer.rect));
-        } else if (content_layer.background_color != SK_ColorTRANSPARENT) {
+        if (content_layer.background_color != SK_ColorBLACK &&
+            content_layer.background_color != SK_ColorTRANSPARENT) {
           return false;
         }
       }
     }
   }
-  background_rect->Scale(1 / scale_factor);
   return found_video_layer;
 }
 
@@ -554,6 +550,7 @@ void CARendererLayerTree::TransformLayer::AddContentLayer(
 
 void CARendererLayerTree::RootLayer::CommitToCA(CALayer* superlayer,
                                                 RootLayer* old_layer,
+                                                const gfx::Size& pixel_size,
                                                 float scale_factor) {
   if (old_layer) {
     DCHECK(old_layer->ca_layer);
@@ -569,8 +566,9 @@ void CARendererLayerTree::RootLayer::CommitToCA(CALayer* superlayer,
     DLOG(ERROR) << "CARendererLayerTree root layer not attached to tree.";
   }
 
-  gfx::RectF bg_rect;
-  if (WantsFullcreenLowPowerBackdrop(scale_factor, &bg_rect)) {
+  if (WantsFullcreenLowPowerBackdrop()) {
+    const gfx::RectF bg_rect(
+        ScaleSize(gfx::SizeF(pixel_size), 1 / scale_factor));
     if (gfx::RectF([ca_layer frame]) != bg_rect)
       [ca_layer setFrame:bg_rect.ToCGRect()];
     if (![ca_layer backgroundColor])