Use float for scroll offset.

third_party/WebKit/Source/platform/scroll/ScrollTypes.h

Index: third_party/WebKit/Source/platform/scroll/ScrollTypes.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollTypes.h b/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
index 15f40c51b53d23e4c8333df420f680eb0d946bf7..0ad3b86099c2cfb31a523ca6e8cfc426dd8fa8ea 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
@@ -26,11 +26,17 @@
 #ifndef ScrollTypes_h
 #define ScrollTypes_h
 
-#include "platform/geometry/FloatSize.h"
+#include "platform/geometry/FloatPoint.h"
 #include "wtf/Assertions.h"
 
 namespace blink {
 
+typedef FloatSize ScrollOffset;
+
+inline ScrollOffset toScrollOffset(const FloatPoint& p) {
+  return ScrollOffset(p.x(), p.y());
+}
+
 enum ScrollDirection {
   ScrollUpIgnoringWritingMode,
   ScrollDownIgnoringWritingMode,
@@ -195,8 +201,8 @@ struct ScrollResult {
         unusedScrollDeltaY(0) {}
   ScrollResult(bool didScrollX,
                bool didScrollY,
-               float unusedScrollDeltaX,
-               float unusedScrollDeltaY)
+               double unusedScrollDeltaX,

[bokan, 2016/10/02 19:47:51]

Shouldn't we keep these as float?

[szager1, 2016/10/05 07:43:36]

Whoops, fixed.

+               double unusedScrollDeltaY)
       : didScrollX(didScrollX),
         didScrollY(didScrollY),
         unusedScrollDeltaX(unusedScrollDeltaX),
@@ -208,21 +214,22 @@ struct ScrollResult {
   bool didScrollY;
 
   // In pixels.
-  float unusedScrollDeltaX;
-  float unusedScrollDeltaY;
+  double unusedScrollDeltaX;
+  double unusedScrollDeltaY;
 };
 
-inline FloatSize toScrollDelta(ScrollbarOrientation orientation, float delta) {
-  return orientation == HorizontalScrollbar ? FloatSize(delta, 0.0f)
-                                            : FloatSize(0.0f, delta);
+inline ScrollOffset toScrollDelta(ScrollbarOrientation orientation,
+                                  double delta) {
+  return orientation == HorizontalScrollbar ? ScrollOffset(delta, 0.0f)
+                                            : ScrollOffset(0.0f, delta);
 }
 
-inline FloatSize toScrollDelta(ScrollDirectionPhysical dir, float delta) {
+inline ScrollOffset toScrollDelta(ScrollDirectionPhysical dir, double delta) {
   if (dir == ScrollUp || dir == ScrollLeft)
     delta = -delta;
 
-  return (dir == ScrollLeft || dir == ScrollRight) ? FloatSize(delta, 0)
-                                                   : FloatSize(0, delta);
+  return (dir == ScrollLeft || dir == ScrollRight) ? ScrollOffset(delta, 0)
+                                                   : ScrollOffset(0, delta);
 }
 
 typedef unsigned ScrollbarControlPartMask;