chromeos: don't allocate LocalSurfaceId if size doesnt change

If WindowTreeHostMus::SetBounds() is called with no LocalSurfaceIdAllocation
(as happens when views calls SetBounds()) and the size hasn't changed, then
the current LocalSurfaceId should be used.

BUG=931878
TEST=covered by test

Change-Id: I135dca75ce04220796c41dd9d49042127d5dcfc5
Reviewed-on: https://chromium-review.googlesource.com/c/1474252
Auto-Submit: Scott Violet <sky@chromium.org>
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632394}

ui/aura/mus/window_tree_host_mus.cc

@@ -208,7 +208,8 @@ void WindowTreeHostMus::SetBounds(
     // OnWindowTreeHostBoundsWillChange().
     if (!local_surface_id_allocation.IsValid() &&
         ShouldAllocateLocalSurfaceIdOnResize()) {
-      window()->AllocateLocalSurfaceId();
+      if (pixel_bounds.size() != compositor()->size())
+        window()->AllocateLocalSurfaceId();
       actual_local_surface_id_allocation =
           window()->GetLocalSurfaceIdAllocation();
     }

ui/aura/mus/window_tree_host_mus_unittest.cc

@@ -4,23 +4,65 @@
 
 #include "ui/aura/mus/window_tree_host_mus.h"
 
+#include "components/viz/common/surfaces/local_surface_id_allocation.h"
+#include "components/viz/common/surfaces/parent_local_surface_id_allocator.h"
 #include "ui/aura/mus/window_port_mus.h"
 #include "ui/aura/mus/window_tree_host_mus_init_params.h"
 #include "ui/aura/test/aura_mus_test_base.h"
 #include "ui/aura/test/mus/test_window_tree.h"
+#include "ui/aura/window.h"
 
 namespace aura {
 
-using WindowTreeHostMusTest = aura::test::AuraMusClientTestBase;
+using WindowTreeHostMusTest = test::AuraMusClientTestBase;
 
 TEST_F(WindowTreeHostMusTest, UpdateClientArea) {
   std::unique_ptr<WindowTreeHostMus> window_tree_host_mus =
       std::make_unique<WindowTreeHostMus>(
-          aura::CreateInitParamsForTopLevel(window_tree_client_impl()));
+          CreateInitParamsForTopLevel(window_tree_client_impl()));
 
   gfx::Insets new_insets(10, 11, 12, 13);
   window_tree_host_mus->SetClientArea(new_insets, std::vector<gfx::Rect>());
   EXPECT_EQ(new_insets, window_tree()->last_client_area());
 }
 
+TEST_F(WindowTreeHostMusTest, DontGenerateNewSurfaceIdOnMove) {
+  std::unique_ptr<WindowTreeHostMus> window_tree_host =
+      std::make_unique<WindowTreeHostMus>(
+          CreateInitParamsForTopLevel(window_tree_client_impl()));
+  window_tree_host->InitHost();
+  Window* window = window_tree_host->window();
+  ws::mojom::WindowDataPtr data = ws::mojom::WindowData::New();
+  data->window_id = WindowMus::Get(window)->server_id();
+  data->visible = true;
+  viz::ParentLocalSurfaceIdAllocator parent_local_surface_id_allocator;
+  parent_local_surface_id_allocator.GenerateId();
+  uint32_t change_id = 0;
+  ASSERT_TRUE(window_tree()->GetAndRemoveFirstChangeOfType(
+      WindowTreeChangeType::NEW_TOP_LEVEL, &change_id));
+  window_tree_client()->OnTopLevelCreated(
+      change_id, std::move(data), 1u, true,
+      parent_local_surface_id_allocator.GetCurrentLocalSurfaceIdAllocation());
+  window_tree_host->SetBounds(gfx::Rect(1, 2, 3, 4),
+                              viz::LocalSurfaceIdAllocation());
+  window_tree()->AckAllChanges();
+  EXPECT_EQ(0u,
+            window_tree()->GetChangeCountForType(WindowTreeChangeType::BOUNDS));
+  const viz::LocalSurfaceIdAllocation lsia =
+      window_tree_host->compositor()->GetLocalSurfaceIdAllocation();
+
+  // Setting the bounds to the same size, but different location should not
+  // generate a new id.
+  window_tree_host->SetBounds(gfx::Rect(1, 21, 3, 4),
+                              viz::LocalSurfaceIdAllocation());
+  EXPECT_EQ(lsia,
+            window_tree_host->compositor()->GetLocalSurfaceIdAllocation());
+  EXPECT_EQ(1u, window_tree()->number_of_changes());
+  EXPECT_EQ(1u,
+            window_tree()->GetChangeCountForType(WindowTreeChangeType::BOUNDS));
+  ASSERT_TRUE(window_tree()->last_local_surface_id());
+  EXPECT_EQ(lsia.local_surface_id(), window_tree()->last_local_surface_id());
+  window_tree()->AckAllChanges();
+}
+
 }  // namespace aura