Make RenderPass::Id an isolated class

cc/output/delegating_renderer_unittest.cc

Index: cc/output/delegating_renderer_unittest.cc
diff --git a/cc/output/delegating_renderer_unittest.cc b/cc/output/delegating_renderer_unittest.cc
index f8e4b69b857e73d29387fe8c8bd6b427a990ce98..99dc395fa298b26d037fb8039832a7b486ced2e5 100644
--- a/cc/output/delegating_renderer_unittest.cc
+++ b/cc/output/delegating_renderer_unittest.cc
@@ -95,19 +95,17 @@ class DelegatingRendererTestResources : public DelegatingRendererTest {
     frame->render_passes.clear();
     frame->render_passes_by_id.clear();
 
-    TestRenderPass* child_pass = AddRenderPass(
-        &frame->render_passes,
-        RenderPass::Id(2, 1),
-        gfx::Rect(3, 3, 10, 10),
-        gfx::Transform());
-    child_pass->AppendOneOfEveryQuadType(
-        host_impl->resource_provider(), RenderPass::Id(0, 0));
+    TestRenderPass* child_pass = AddRenderPass(&frame->render_passes,
+                                               RenderPassId(2, 1),
+                                               gfx::Rect(3, 3, 10, 10),
+                                               gfx::Transform());
+    child_pass->AppendOneOfEveryQuadType(host_impl->resource_provider(),
+                                         RenderPassId(0, 0));
 
-    TestRenderPass* pass = AddRenderPass(
-        &frame->render_passes,
-        RenderPass::Id(1, 1),
-        gfx::Rect(3, 3, 10, 10),
-        gfx::Transform());
+    TestRenderPass* pass = AddRenderPass(&frame->render_passes,
+                                         RenderPassId(1, 1),
+                                         gfx::Rect(3, 3, 10, 10),
+                                         gfx::Transform());
     pass->AppendOneOfEveryQuadType(
         host_impl->resource_provider(), child_pass->id);
     return draw_result;