cc: Add support for partial swaps when using impl-side painting.

cc/resources/tile_manager.cc

Index: cc/resources/tile_manager.cc
diff --git a/cc/resources/tile_manager.cc b/cc/resources/tile_manager.cc
index 809301fc5fcd92a056cc92cc82534caf1c71084b..fc18c14421debc4a24c2142f1eeabf07e6996fe8 100644
--- a/cc/resources/tile_manager.cc
+++ b/cc/resources/tile_manager.cc
@@ -12,6 +12,7 @@
 #include "base/json/json_writer.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
+#include "cc/base/math_util.h"
 #include "cc/debug/devtools_instrumentation.h"
 #include "cc/debug/traced_value.h"
 #include "cc/layers/picture_layer_impl.h"
@@ -462,6 +463,7 @@ TileManager::TileManager(
   };
   raster_worker_pool_delegate_ = RasterWorkerPoolDelegate::Create(
       this, raster_worker_pools, arraysize(raster_worker_pools));
+  damage_rect_ = gfx::Rect(0, 0, 0, 0);
 }
 
 TileManager::~TileManager() {
@@ -490,6 +492,7 @@ TileManager::~TileManager() {
     (*it)->DidUnregisterLayer();
   }
   layers_.clear();
+  tilemap_.clear();
 }
 
 void TileManager::Release(Tile* tile) {
@@ -497,6 +500,16 @@ void TileManager::Release(Tile* tile) {
   released_tiles_.push_back(tile);
 }
 
+void TileManager::ResetTileRectLayerMap() {
+  for (std::map<int, gfx::Rect>::iterator it = tilemap_.begin();
+       it != tilemap_.end();
+       ++it) {
+    it->second = gfx::Rect(0, 0, 0, 0);
+  }
+}

[reveman, 2014/04/11 18:11:34]

all this tilemap stuff is confusing and inefficient. please notify the client as
tiles get initialized instead.

[sohanjg, 2014/04/14 10:16:11]

Done.

+
+std::map<int, gfx::Rect> TileManager::GetTileRectLayerMap() { return tilemap_; }
+
 void TileManager::DidChangeTilePriority(Tile* tile) {
   prioritized_tiles_dirty_ = true;
 }
@@ -1232,6 +1245,10 @@ void TileManager::OnRasterTaskCompleted(
     return;
   }
 
+  // Maintain a map of unioned intialized tile rect and layer-id.
+  tilemap_[tile->layer_id()] =
+      gfx::UnionRects(tilemap_[tile->layer_id()], tile->content_rect());
+
   ++update_visible_tiles_stats_.completed_count;
 
   tile_version.set_has_text(analysis.has_text);