Use a struct for cc::Surface ids for more type safety

cc/quads/surface_draw_quad.cc

Index: cc/quads/surface_draw_quad.cc
diff --git a/cc/quads/surface_draw_quad.cc b/cc/quads/surface_draw_quad.cc
index e7d09d5efcaf344636b21e321b26bcdde96b9358..8591261c2dec2446e0e70af9b33e9c1919eea8e7 100644
--- a/cc/quads/surface_draw_quad.cc
+++ b/cc/quads/surface_draw_quad.cc
@@ -9,7 +9,8 @@
 
 namespace cc {
 
-SurfaceDrawQuad::SurfaceDrawQuad() : surface_id(0) {}
+SurfaceDrawQuad::SurfaceDrawQuad() {
+}
 
 scoped_ptr<SurfaceDrawQuad> SurfaceDrawQuad::Create() {
   return make_scoped_ptr(new SurfaceDrawQuad);
@@ -18,7 +19,7 @@ scoped_ptr<SurfaceDrawQuad> SurfaceDrawQuad::Create() {
 void SurfaceDrawQuad::SetNew(const SharedQuadState* shared_quad_state,
                              const gfx::Rect& rect,
                              const gfx::Rect& visible_rect,
-                             int surface_id) {
+                             SurfaceId surface_id) {
   gfx::Rect opaque_rect;
   bool needs_blending = false;
   DrawQuad::SetAll(shared_quad_state, DrawQuad::SURFACE_CONTENT, rect,
@@ -31,7 +32,7 @@ void SurfaceDrawQuad::SetAll(const SharedQuadState* shared_quad_state,
                              const gfx::Rect& opaque_rect,
                              const gfx::Rect& visible_rect,
                              bool needs_blending,
-                             int surface_id) {
+                             SurfaceId surface_id) {
   DrawQuad::SetAll(shared_quad_state, DrawQuad::SURFACE_CONTENT, rect,
                    opaque_rect, visible_rect, needs_blending);
   this->surface_id = surface_id;
@@ -46,7 +47,7 @@ const SurfaceDrawQuad* SurfaceDrawQuad::MaterialCast(const DrawQuad* quad) {
 }
 
 void SurfaceDrawQuad::ExtendValue(base::DictionaryValue* value) const {
-  value->SetInteger("surface_id", surface_id);
+  value->SetInteger("surface_id", surface_id.id);
 }