[DevTools] Initial implementation of device modes.

Source/devtools/front_end/main/Main.js

Index: Source/devtools/front_end/main/Main.js
diff --git a/Source/devtools/front_end/main/Main.js b/Source/devtools/front_end/main/Main.js
index 141bfb5edbc8a3d1962681734375eef270a139d7..78b8f80805e7361ee30240ccb48b0bc68ad0d685 100644
--- a/Source/devtools/front_end/main/Main.js
+++ b/Source/devtools/front_end/main/Main.js
@@ -127,6 +127,7 @@ WebInspector.Main.prototype = {
         Runtime.experiments.register("blackboxJSFramesOnTimeline", "Blackbox JavaScript frames on Timeline");
         Runtime.experiments.register("timelineDetailsChart", "Costly functions view in Timeline details", true);
         Runtime.experiments.register("customObjectFormatters", "Custom object formatters", true);
+        Runtime.experiments.register("deviceModes", "Device variations in Device Mode", true);
         Runtime.experiments.register("emptySourceMapAutoStepping", "Empty sourcemap auto-stepping");
         Runtime.experiments.register("fileSystemInspection", "FileSystem inspection");
         Runtime.experiments.register("filmStripInNetworkAndTimeline", "Filmstrip in Network and Timeline Panel", true);