Add support for calculating the position of the top controls in the cc layer.

cc/layer_tree_settings.cc

Index: cc/layer_tree_settings.cc
diff --git a/cc/layer_tree_settings.cc b/cc/layer_tree_settings.cc
index 4221167c29fa139a0ed67d473ea6deccda6bc79e..8eba4f606097c452e2dba547b4ff2d0bc7008cf9 100644
--- a/cc/layer_tree_settings.cc
+++ b/cc/layer_tree_settings.cc
@@ -26,9 +26,11 @@ LayerTreeSettings::LayerTreeSettings()
     , showOverdrawInTracing(false)
     , canUseLCDText(true)
     , shouldClearRootRenderPass(true)
+    , calculateTopControlsPosition(false)
     , refreshRate(0)
     , maxPartialTextureUpdates(std::numeric_limits<size_t>::max())
     , numRasterThreads(1)
+    , topControlsHeight(0)
     , defaultTileSize(gfx::Size(256, 256))
     , maxUntiledLayerSize(gfx::Size(512, 512))
     , minimumOcclusionTrackingSize(gfx::Size(160, 160))
@@ -40,6 +42,19 @@ LayerTreeSettings::LayerTreeSettings()
     backgroundColorInsteadOfCheckerboard = CommandLine::ForCurrentProcess()->HasSwitch(switches::kBackgroundColorInsteadOfCheckerboard);
     showOverdrawInTracing = CommandLine::ForCurrentProcess()->HasSwitch(switches::kTraceOverdraw);
 
+    calculateTopControlsPosition = CommandLine::ForCurrentProcess()->HasSwitch(switches::kEnableTopControlsPositionCalculation);
+    if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kTopControlsHeight)) {
+        std::string controls_height_str =
+            CommandLine::ForCurrentProcess()->GetSwitchValueASCII(switches::kTopControlsHeight);
+        int controls_height;
+        if (base::StringToInt(controls_height_str, &controls_height) && controls_height > 0)
+            topControlsHeight = controls_height;
+    }
+    if (calculateTopControlsPosition && (topControlsHeight <= 0 || !compositorFrameMessage)) {
+        DCHECK(false) << "Top controls repositioning enabled without valid height or compositorFrameMessage set.";
+        calculateTopControlsPosition = false;
+    }
+
 // TODO(alokp): Remove this hard-coded setting.
 // Platforms that need to disable LCD text must explicitly set this value.
 #if defined(OS_ANDROID)