Add gfx StructTraits for ScrollOffset.

To support synchronous compositor for Android webview over mojo add
a struct trait for ScrollOffset

BUG=722928
TBR=vollick@chromium.org

Change-Id: I4138ac3ff93fc17e6a123335ac3a82975df48db4
Reviewed-on: https://chromium-review.googlesource.com/830115
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524713}

ui/gfx/geometry/mojo/OWNERS

@@ -3,3 +3,6 @@ per-file *_struct_traits*.*=file://ipc/SECURITY_OWNERS
 
 per-file *.mojom=set noparent
 per-file *.mojom=file://ipc/SECURITY_OWNERS
+
+per-file *.typemap=set noparent
+per-file *.typemap=file://ipc/SECURITY_OWNERS

ui/gfx/geometry/mojo/geometry.mojom

@@ -68,3 +68,8 @@ struct Vector2dF {
   float x;
   float y;
 };
+
+struct ScrollOffset {
+  float x;
+  float y;
+};

ui/gfx/geometry/mojo/geometry.typemap

@@ -10,6 +10,7 @@ public_headers = [
   "//ui/gfx/geometry/rect.h",
   "//ui/gfx/geometry/rect_f.h",
   "//ui/gfx/geometry/safe_integer_conversions.h",
+  "//ui/gfx/geometry/scroll_offset.h",
   "//ui/gfx/geometry/insets.h",
   "//ui/gfx/geometry/vector2d.h",
   "//ui/gfx/geometry/vector2d_f.h",
@@ -29,4 +30,5 @@ type_mappings = [
   "gfx.mojom.InsetsF=gfx::InsetsF",
   "gfx.mojom.Vector2d=gfx::Vector2d",
   "gfx.mojom.Vector2dF=gfx::Vector2dF",
+  "gfx.mojom.ScrollOffset=gfx::ScrollOffset",
 ]

ui/gfx/geometry/mojo/geometry_struct_traits.h

@@ -12,6 +12,7 @@
 #include "ui/gfx/geometry/point_f.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_f.h"
+#include "ui/gfx/geometry/scroll_offset.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/geometry/size_f.h"
 #include "ui/gfx/geometry/vector2d.h"
@@ -141,6 +142,18 @@ struct StructTraits<gfx::mojom::Vector2dFDataView, gfx::Vector2dF> {
   }
 };
 
+template <>
+struct StructTraits<gfx::mojom::ScrollOffsetDataView, gfx::ScrollOffset> {
+  static float x(const gfx::ScrollOffset& v) { return v.x(); }
+  static float y(const gfx::ScrollOffset& v) { return v.y(); }
+  static bool Read(gfx::mojom::ScrollOffsetDataView data,
+                   gfx::ScrollOffset* out) {
+    out->set_x(data.x());
+    out->set_y(data.y());
+    return true;
+  }
+};
+
 }  // namespace mojo
 
 #endif  // UI_GFX_GEOMETRY_MOJO_GEOMETRY_STRUCT_TRAITS_H_