Add SurfaceId::id_namespace()

This ties SurfaceIdAllocator to SurfaceId, such that it is now the only
valid allocator for SurfaceIds.

R=jbauman@chromium.org
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1834583004

Cr-Commit-Position: refs/heads/master@{#383323}

2 files changed, 17 insertions, 0 deletions

diff --git a/cc/surfaces/surface_id.h b/cc/surfaces/surface_id.h
index c0c4410..bbc485f 100644
--- a/cc/surfaces/surface_id.h
+++ b/cc/surfaces/surface_id.h
@@ -18,6 +18,9 @@ struct SurfaceId {
 
   bool is_null() const { return id == 0; }
 
+  // See SurfaceIdAllocator::GenerateId.
+  uint32_t id_namespace() const { return id >> 32; }
+
   uint64_t id;
 };
 
diff --git a/cc/surfaces/surface_unittest.cc b/cc/surfaces/surface_unittest.cc
index 72070c6..03ffc3a 100644
--- a/cc/surfaces/surface_unittest.cc
+++ b/cc/surfaces/surface_unittest.cc
@@ -5,6 +5,7 @@
 #include "cc/surfaces/surface.h"
 #include "cc/surfaces/surface_factory.h"
 #include "cc/surfaces/surface_factory_client.h"
+#include "cc/surfaces/surface_id_allocator.h"
 #include "cc/surfaces/surface_manager.h"
 #include "cc/test/scheduler_test_common.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -44,5 +45,18 @@ TEST(SurfaceTest, SurfaceLifetime) {
   EXPECT_EQ(NULL, manager.GetSurfaceForId(surface_id));
 }
 
+TEST(SurfaceTest, SurfaceIds) {
+  uint32_t namespaces[] = {0u, 37u, ~0u};
+  for (size_t i = 0; i < 3; ++i) {
+    uint32_t id_namespace = namespaces[i];
+    SurfaceIdAllocator allocator(id_namespace);
+    SurfaceId id1 = allocator.GenerateId();
+    EXPECT_EQ(id1.id_namespace(), id_namespace);
+    SurfaceId id2 = allocator.GenerateId();
+    EXPECT_EQ(id2.id_namespace(), id_namespace);
+    EXPECT_NE(id1.id, id2.id);
+  }
+}
+
 }  // namespace
 }  // namespace cc