LayerTreeHost should not modify the LayerTreeSettings object.

Instead it should use a temporary variable wherever needed and
leave the settings object const.  This patch removes the last
instance of this behavior and makes the settings object const.

BUG=234233

Review URL: https://codereview.chromium.org/23463042

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227149 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 19 insertions, 17 deletions

diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 34f4d2f..7bece08 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -205,16 +205,6 @@ LayerTreeHost::OnCreateAndInitializeOutputSurfaceAttempted(bool success) {
   if (success) {
     output_surface_lost_ = false;
 
-    // Update settings_ based on partial update capability.
-    size_t max_partial_texture_updates = 0;
-    if (proxy_->GetRendererCapabilities().allow_partial_texture_updates &&
-        !settings_.impl_side_painting) {
-      max_partial_texture_updates = std::min(
-          settings_.max_partial_texture_updates,
-          proxy_->MaxPartialTextureUpdates());
-    }
-    settings_.max_partial_texture_updates = max_partial_texture_updates;
-
     if (!contents_texture_manager_ &&
         (!settings_.impl_side_painting || !settings_.solid_color_scrollbars)) {
       contents_texture_manager_ =
@@ -1124,8 +1114,19 @@ bool LayerTreeHost::AlwaysUsePartialTextureUpdates() {
   return !proxy_->HasImplThread();
 }
 
+size_t LayerTreeHost::MaxPartialTextureUpdates() const {
+  size_t max_partial_texture_updates = 0;
+  if (proxy_->GetRendererCapabilities().allow_partial_texture_updates &&
+      !settings_.impl_side_painting) {
+    max_partial_texture_updates =
+        std::min(settings_.max_partial_texture_updates,
+                 proxy_->MaxPartialTextureUpdates());
+  }
+  return max_partial_texture_updates;
+}
+
 bool LayerTreeHost::RequestPartialTextureUpdate() {
-  if (partial_texture_update_requests_ >= settings_.max_partial_texture_updates)
+  if (partial_texture_update_requests_ >= MaxPartialTextureUpdates())
     return false;
 
   partial_texture_update_requests_++;
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index f34215f..d92200f 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -273,6 +273,7 @@ class CC_EXPORT LayerTreeHost : NON_EXPORTED_BASE(public RateLimiterClient) {
   virtual void RateLimit() OVERRIDE;
 
   bool AlwaysUsePartialTextureUpdates();
+  size_t MaxPartialTextureUpdates() const;
   bool RequestPartialTextureUpdate();
 
   void SetDeviceScaleFactor(float device_scale_factor);
@@ -386,7 +387,7 @@ class CC_EXPORT LayerTreeHost : NON_EXPORTED_BASE(public RateLimiterClient) {
   base::WeakPtr<InputHandler> input_handler_weak_ptr_;
   base::WeakPtr<TopControlsManager> top_controls_manager_weak_ptr_;
 
-  LayerTreeSettings settings_;
+  const LayerTreeSettings settings_;
   LayerTreeDebugState debug_state_;
 
   gfx::Size device_viewport_size_;
diff --git a/cc/trees/layer_tree_host_unittest.cc b/cc/trees/layer_tree_host_unittest.cc
index 904b37e..aef9f35 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -2116,7 +2116,7 @@ TEST(LayerTreeHostTest, LimitPartialUpdates) {
     LayerTreeHostWithProxy host(&client, settings, proxy.Pass());
     EXPECT_TRUE(host.InitializeOutputSurfaceIfNeeded());
 
-    EXPECT_EQ(0u, host.settings().max_partial_texture_updates);
+    EXPECT_EQ(0u, host.MaxPartialTextureUpdates());
   }
 
   // When partial updates are allowed,
@@ -2134,7 +2134,7 @@ TEST(LayerTreeHostTest, LimitPartialUpdates) {
     LayerTreeHostWithProxy host(&client, settings, proxy.Pass());
     EXPECT_TRUE(host.InitializeOutputSurfaceIfNeeded());
 
-    EXPECT_EQ(5u, host.settings().max_partial_texture_updates);
+    EXPECT_EQ(5u, host.MaxPartialTextureUpdates());
   }
 
   // When partial updates are allowed,
@@ -2152,7 +2152,7 @@ TEST(LayerTreeHostTest, LimitPartialUpdates) {
     LayerTreeHostWithProxy host(&client, settings, proxy.Pass());
     EXPECT_TRUE(host.InitializeOutputSurfaceIfNeeded());
 
-    EXPECT_EQ(10u, host.settings().max_partial_texture_updates);
+    EXPECT_EQ(10u, host.MaxPartialTextureUpdates());
   }
 }
 
@@ -2189,7 +2189,7 @@ TEST(LayerTreeHostTest, PartialUpdatesWithDelegatingRendererAndGLContent) {
   scoped_ptr<LayerTreeHost> host =
       LayerTreeHost::Create(&client, settings, NULL);
   EXPECT_TRUE(host->InitializeOutputSurfaceIfNeeded());
-  EXPECT_EQ(0u, host->settings().max_partial_texture_updates);
+  EXPECT_EQ(0u, host->MaxPartialTextureUpdates());
 }
 
 TEST(LayerTreeHostTest,
@@ -2202,7 +2202,7 @@ TEST(LayerTreeHostTest,
   scoped_ptr<LayerTreeHost> host =
       LayerTreeHost::Create(&client, settings, NULL);
   EXPECT_TRUE(host->InitializeOutputSurfaceIfNeeded());
-  EXPECT_EQ(0u, host->settings().max_partial_texture_updates);
+  EXPECT_EQ(0u, host->MaxPartialTextureUpdates());
 }
 
 class LayerTreeHostTestShutdownWithOnlySomeResourcesEvicted