Expose FS show/hide thresholds to Command Line

cc/switches.cc

Index: cc/switches.cc
diff --git a/cc/switches.cc b/cc/switches.cc
index ec74e8394838ed3652b4fa8c4e57244548217096..9b57c583db5dd78fc1908232cf6ebe12ed0ad274 100644
--- a/cc/switches.cc
+++ b/cc/switches.cc
@@ -33,6 +33,12 @@ const char kEnableTopControlsPositionCalculation[] =
 // The height of the movable top controls.
 const char kTopControlsHeight[] = "top-controls-height";
 
+// Percentage of the top controls need to be hidden before they will auto hide.
+const char kTopControlsHideThreshold[] = "top-controls-hide-threshold";
+
+// Percentage of the top controls need to be shown before they will auto show.
+const char kTopControlsShowThreshold[] = "top-controls-show-threshold";
+
 // Number of worker threads used to rasterize content.
 const char kNumRasterThreads[] = "num-raster-threads";