The WebInspector.sendOverProtocol method provides an easy mechanism to test

and debug protocol commands. It's intended for developer debugging only.

Examples:

    WebInspector.sendOverProtocol('Emulation.setDeviceMetricsOverride', { ... });
    WebInspector.sendOverProtocol('Emulation.clearDeviceMetricsOverride');

    WebInspector.sendOverProtocol('Page.captureScreenshot')
        .then((err, result) => console.log(result));

Review-Url: https://codereview.chromium.org/2149833002
Cr-Commit-Position: refs/heads/master@{#405625}

third_party/WebKit/Source/devtools/front_end/main/Main.js

@@ -949,6 +949,23 @@ WebInspector.Main.InspectedNodeRevealer.prototype = {
     }
 }
 
+/**
+ * @param {string} method
+ * @param {?Object} params
+ * @return {!Promise}
+ */
+WebInspector.sendOverProtocol = function(method, params)
+{
+    var connection = WebInspector.targetManager.mainTarget().connection();
+    return new Promise((resolve, reject) => {
+        connection.sendRawMessageForTesting(method, params, (err, result) => {
+            if (err)
+                return reject(err);
+            return resolve(result);
+        });
+    });
+}
+
 /**
  * @constructor
  * @extends {WebInspector.VBox}

third_party/WebKit/Source/devtools/front_end/sdk/InspectorBackend.js

@@ -317,6 +317,17 @@ InspectorBackendClass.Connection.prototype = {
         throw "Not implemented";
     },
 
+    /**
+     * @param {string} method
+     * @param {?Object} params
+     * @param {?function(*)} callback
+     */
+    sendRawMessageForTesting: function(method, params, callback)
+    {
+        var domain = method.split(".")[0];
+        this._wrapCallbackAndSendMessageObject(domain, method, params, callback);
+    },
+
     /**
      * @param {!Object|string} message
      */

third_party/WebKit/Source/devtools/front_end/sdk/Target.js

@@ -74,6 +74,15 @@ WebInspector.Target.prototype = {
         return (this._capabilitiesMask & capabilitiesMask) === capabilitiesMask;
     },
 
+    /**
+     *
+     * @return {!InspectorBackendClass.Connection}
+     */
+    connection: function()
+    {
+        return this._connection;
+    },
+
     /**
      * @param {string} label
      * @return {string}