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 f8b964307a539c30527ac2d1701c903def2912a8..20ccd6917ea3a688e00ef0e4d3de24595cc2cfb7 100644
--- a/cc/layer_tree_settings.cc
+++ b/cc/layer_tree_settings.cc
@@ -27,9 +27,11 @@ LayerTreeSettings::LayerTreeSettings()
     , canUseLCDText(true)
     , shouldClearRootRenderPass(true)
     , useLinearFadeScrollbarAnimator(false)
+    , calculateTopControlsPosition(false)
     , refreshRate(0)
     , maxPartialTextureUpdates(std::numeric_limits<size_t>::max())
     , numRasterThreads(1)
+    , topControlsHeightPx(0)
     , defaultTileSize(gfx::Size(256, 256))
     , maxUntiledLayerSize(gfx::Size(512, 512))
     , minimumOcclusionTrackingSize(gfx::Size(160, 160))
@@ -41,6 +43,19 @@ LayerTreeSettings::LayerTreeSettings()
     backgroundColorInsteadOfCheckerboard = CommandLine::ForCurrentProcess()->HasSwitch(switches::kBackgroundColorInsteadOfCheckerboard);
     showOverdrawInTracing = CommandLine::ForCurrentProcess()->HasSwitch(switches::kTraceOverdraw);
 
+    calculateTopControlsPosition = CommandLine::ForCurrentProcess()->HasSwitch(switches::kEnableTopControlsPositionCalculation);

[jamesr, 2013/01/08 02:26:48]

I don't understand how this could work for both the browser and render process
embeddings of cc, since they'll have the same command line flags but you don't
want both to have the top controls stuff.  Rather than checking the command line
flags here in cc/switches.cc, you should check whichever flags you care about in
the code embedding cc/ and set the LayerTreeHostSettings there

[Ted C, 2013/01/08 18:17:33]

Hmm...so move this check to web_layer_tree_view_impl?  It doesn't look to be
doing anything like this there currently, so I just wanted to confirm that is
the right place.  That is until your change lands and it gets refactored into
render_widget, which I guess it would go there instead.

[Ted C, 2013/01/09 23:36:01]

I just uploaded a patch where I moved it to web_layer_tree_view_impl.  Let me
know if that isn't the right place.

+    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)
+            topControlsHeightPx = controls_height;
+    }
+    if (calculateTopControlsPosition && (topControlsHeightPx <= 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)