Make scroll offset type of float in cc

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index eed1e5a7e151e74942e0b78d54b96f38a2f2874d..c514a904fc6fa503b6e48664fa3f58bd59013ba9 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -40,6 +40,7 @@
 #include "cc/trees/single_thread_proxy.h"
 #include "cc/trees/thread_proxy.h"
 #include "cc/trees/tree_synchronizer.h"
+#include "ui/gfx/geometry/vector2d_conversions.h"
 #include "ui/gfx/size_conversions.h"
 
 namespace {
@@ -1066,8 +1067,8 @@ void LayerTreeHost::ApplyScrollAndScale(ScrollAndScaleSet* info) {
     QueueSwapPromise(swap_promise.Pass());
   }
 
-  gfx::Vector2d inner_viewport_scroll_delta;
-  gfx::Vector2d outer_viewport_scroll_delta;
+  gfx::Vector2dF inner_viewport_scroll_delta;
+  gfx::Vector2dF outer_viewport_scroll_delta;
 
   for (size_t i = 0; i < info->scrolls.size(); ++i) {
     Layer* layer = LayerTreeHostCommon::FindLayerInSubtree(
@@ -1106,8 +1107,12 @@ void LayerTreeHost::ApplyScrollAndScale(ScrollAndScaleSet* info) {
     }
     ApplyPageScaleDeltaFromImplSide(info->page_scale_delta);
 
+    // TODO(miletus@): make viewport delta Vector2DF.

[danakj, 2014/09/18 21:21:52]

nit: no @, capital M

[Yufeng Shen (Slow to review), 2014/09/18 22:47:55]

Done.

+    gfx::Vector2d viewport_scroll_delta = gfx::ToFlooredVector2d(
+        inner_viewport_scroll_delta + outer_viewport_scroll_delta);
+
     client_->ApplyViewportDeltas(
-        inner_viewport_scroll_delta + outer_viewport_scroll_delta,
+        viewport_scroll_delta,
         info->page_scale_delta,
         info->top_controls_delta);
   }