Make PointerEvent coordinates fractional for touch

third_party/WebKit/Source/core/events/MouseEvent.idl

Index: third_party/WebKit/Source/core/events/MouseEvent.idl
diff --git a/third_party/WebKit/Source/core/events/MouseEvent.idl b/third_party/WebKit/Source/core/events/MouseEvent.idl
index 99172320ccde0916bcc8fa2e4c02ff2422be5254..66c1ce6e788fde1527545bc6098d187392f049e4 100644
--- a/third_party/WebKit/Source/core/events/MouseEvent.idl
+++ b/third_party/WebKit/Source/core/events/MouseEvent.idl
@@ -23,10 +23,10 @@
     Constructor(DOMString type, optional MouseEventInit eventInitDict),
     ConstructorCallWith=ScriptState,
 ] interface MouseEvent : UIEvent {
-    readonly attribute long             screenX;
-    readonly attribute long             screenY;
-    readonly attribute long             clientX;
-    readonly attribute long             clientY;
+    readonly attribute double           screenX;
+    readonly attribute double           screenY;
+    readonly attribute double           clientX;
+    readonly attribute double           clientY;
     readonly attribute boolean          ctrlKey;
     readonly attribute boolean          shiftKey;
     readonly attribute boolean          altKey;
@@ -56,8 +56,7 @@
 
     // CSSOM View Module
     // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-mouseevent-interface
-    // TODO(foolip): These attributes should be of type double, and the spec
-    // also redefines screenX/Y and clientX/Y as double.
+    // TODO(foolip): These attributes should be of type double.
     readonly attribute long pageX;
     readonly attribute long pageY;

[Rick Byers, 2016/10/13 19:08:21]

the Touch page* co-ordinates are double today, so we should upgrade those as
well here.

Maybe just do them all?  It seems weird to change some of the co-ordinates and
not others.  If there's a good reason to delay the ones below though (i.e. if it
complicates the CL much) then I'm OK doing them separately.

[mustaq, 2016/10/14 14:26:58]

Let's do them separately, to minimize MouseEvent related risks.

     [MeasureAs=MouseEventX] readonly attribute long x;