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..f81627b299dd833eff0960b24dacd435f12145a7 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"

[danakj, 2014/09/27 00:00:44]

unused?

[Yufeng Shen (Slow to review), 2014/09/29 19:27:33]

Done.

 #include "ui/gfx/size_conversions.h"
 
 namespace {
@@ -1079,8 +1080,9 @@ void LayerTreeHost::ApplyScrollAndScale(ScrollAndScaleSet* info) {
     } else if (layer == inner_viewport_scroll_layer_.get()) {
       inner_viewport_scroll_delta += info->scrolls[i].scroll_delta;
     } else {
-      layer->SetScrollOffsetFromImplSide(layer->scroll_offset() +
-                                         info->scrolls[i].scroll_delta);
+      layer->SetScrollOffsetFromImplSide(
+          layer->scroll_offset() +

[danakj, 2014/09/27 00:00:44]

ScrollOffsetWithDelta

[Yufeng Shen (Slow to review), 2014/09/29 19:27:33]

Done.

+          gfx::ScrollOffset(info->scrolls[i].scroll_delta));
     }
   }
 
@@ -1097,12 +1099,14 @@ void LayerTreeHost::ApplyScrollAndScale(ScrollAndScaleSet* info) {
     DCHECK(inner_viewport_scroll_layer_.get());  // We should always have this.
 
     inner_viewport_scroll_layer_->SetScrollOffsetFromImplSide(
-        inner_viewport_scroll_layer_->scroll_offset() +
-        inner_viewport_scroll_delta);
+        gfx::ScrollOffsetWithDelta(
+            inner_viewport_scroll_layer_->scroll_offset(),
+            inner_viewport_scroll_delta));
     if (outer_viewport_scroll_layer_.get()) {
       outer_viewport_scroll_layer_->SetScrollOffsetFromImplSide(
-          outer_viewport_scroll_layer_->scroll_offset() +
-          outer_viewport_scroll_delta);
+          gfx::ScrollOffsetWithDelta(
+              outer_viewport_scroll_layer_->scroll_offset(),
+              outer_viewport_scroll_delta));
     }
     ApplyPageScaleDeltaFromImplSide(info->page_scale_delta);