DevTools: allow injecting stylesheets as themes.

Source/devtools/front_end/ExtensionServer.js

Index: Source/devtools/front_end/ExtensionServer.js
diff --git a/Source/devtools/front_end/ExtensionServer.js b/Source/devtools/front_end/ExtensionServer.js
index 1ba95ea0f282f80e055f084380547e3bf1202270..7b348bb1c2905c9dbd6eca884caeef5444c82932 100644
--- a/Source/devtools/front_end/ExtensionServer.js
+++ b/Source/devtools/front_end/ExtensionServer.js
@@ -50,6 +50,7 @@ WebInspector.ExtensionServer = function()
     this._registerHandler(commands.AddAuditResult, this._onAddAuditResult.bind(this));
     this._registerHandler(commands.AddConsoleMessage, this._onAddConsoleMessage.bind(this));
     this._registerHandler(commands.AddRequestHeaders, this._onAddRequestHeaders.bind(this));
+    this._registerHandler(commands.ApplyStyleSheet, this._onApplyStyleSheet.bind(this));
     this._registerHandler(commands.CreatePanel, this._onCreatePanel.bind(this));
     this._registerHandler(commands.CreateSidebarPane, this._onCreateSidebarPane.bind(this));
     this._registerHandler(commands.CreateStatusBarButton, this._onCreateStatusBarButton.bind(this));
@@ -195,6 +196,15 @@ WebInspector.ExtensionServer.prototype = {
         NetworkAgent.setExtraHTTPHeaders(allHeaders);
     },
 
+    _onApplyStyleSheet: function(message)
+    {
+        if (!WebInspector.experimentsSettings.applyCustomStylesheet.isEnabled())
+            return;
+        var styleSheet = document.createElement("style");
+        styleSheet.textContent = message.styleSheet;
+        document.head.appendChild(styleSheet);
+    },
+
     _onCreatePanel: function(message, port)
     {
         var id = message.id;