Tiling priorities in Android Webview.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 94b8bfa1cfac7e9daaa5cef94a4e41954d7a8880..1b66665b57245c8a2719cdf30c98e2a7f6e79834 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1345,16 +1345,27 @@ void LayerTreeHostImpl::SetExternalDrawConstraints(
     const gfx::Transform& transform,
     const gfx::Rect& viewport,
     const gfx::Rect& clip,
+    const gfx::Rect& device_rect_for_tiling,
     bool resourceless_software_draw) {
   if (external_transform_ != transform || external_viewport_ != viewport ||
       resourceless_software_draw_ != resourceless_software_draw) {
     active_tree_->set_needs_update_draw_properties();
   }
 
-  external_transform_ = transform;
   external_viewport_ = viewport;
   external_clip_ = clip;
   resourceless_software_draw_ = resourceless_software_draw;
+
+  // |external_transform_| for Android WebView child compositor hardware draw
+  // is an identity matrix. For software draw, |external_transform_| is what's
+  // passed in.
+  if (!resourceless_software_draw_) {
+    external_transform_ = gfx::Transform();
+    external_viewport_rect_for_tiling_ = device_rect_for_tiling;
+    external_transform_for_tiling_ = transform;

[aelias_OOO_until_Jul13, 2014/07/16 00:32:56]

I find it confusing to repurpose the "transform" argument for two completely
different things depending on mode.  Please add a new argument for tiling
transform to SetExternalDrawConstraints (and throughout the call stack from
android_webview) instead.

[hush (inactive), 2014/07/16 20:45:32]

I added external_tiling_transform as the parameter.
On 2014/07/16 00:32:56, aelias wrote:

+  } else {
+    external_transform_ = transform;
+  }
 }
 
 void LayerTreeHostImpl::SetNeedsRedrawRect(const gfx::Rect& damage_rect) {
@@ -2166,6 +2177,18 @@ gfx::Size LayerTreeHostImpl::DrawViewportSize() const {
   return DeviceViewport().size();
 }
 
+gfx::Rect LayerTreeHostImpl::TilingViewportRect() const {
+  gfx::Rect empty;
+  if (empty == external_viewport_rect_for_tiling_)
+    return gfx::Rect(DrawViewportSize());
+
+  return external_viewport_rect_for_tiling_;
+}
+
+const gfx::Transform& LayerTreeHostImpl::TilingTransform() const {
+  return external_transform_for_tiling_;
+}
+
 gfx::Rect LayerTreeHostImpl::DeviceViewport() const {
   if (external_viewport_.IsEmpty())
     return gfx::Rect(device_viewport_size_);