cc: Remove tile sharing from tilings.

This patch removes sharing tiles from tilings. Previously, tiles
that were not invalidated were shared between the pending and
the active trees. With this patch, tiles that are exist on the
active tree and are not invalidated are not created on the pending
tree, resulting in fewer overall tiles. This improves performance
of updating and managing tiles.

Also, this patch opens up opportunities for a lot of code clean
up that can otherwise be confusing when two trees are involved.

R=danakj, enne

Review URL: https://codereview.chromium.org/1051993002

Cr-Commit-Position: refs/heads/master@{#326804}

2 files changed, 4 insertions, 0 deletions

diff --git a/cc/base/tiling_data.cc b/cc/base/tiling_data.cc
index c9b2fd9..cf2bb57 100644
--- a/cc/base/tiling_data.cc
+++ b/cc/base/tiling_data.cc
@@ -418,6 +418,9 @@ bool TilingData::BaseDifferenceIterator::HasConsiderRect() const {
   return consider_left_ != -1;
 }
 
+TilingData::DifferenceIterator::DifferenceIterator() {
+}
+
 TilingData::DifferenceIterator::DifferenceIterator(
     const TilingData* tiling_data,
     const gfx::Rect& consider_rect,
diff --git a/cc/base/tiling_data.h b/cc/base/tiling_data.h
index a35be59..c95a672 100644
--- a/cc/base/tiling_data.h
+++ b/cc/base/tiling_data.h
@@ -132,6 +132,7 @@ class CC_EXPORT TilingData {
   // with |consider| but which also do not intersect with |ignore|.
   class CC_EXPORT DifferenceIterator : public BaseDifferenceIterator {
    public:
+    DifferenceIterator();
     DifferenceIterator(const TilingData* tiling_data,
                        const gfx::Rect& consider_rect,
                        const gfx::Rect& ignore_rect);