DevTools: add support for chunked protocol messages.

Source/devtools/front_end/sdk/InspectorBackend.js

Index: Source/devtools/front_end/sdk/InspectorBackend.js
diff --git a/Source/devtools/front_end/sdk/InspectorBackend.js b/Source/devtools/front_end/sdk/InspectorBackend.js
index 863bf40be30db6db9ee6d88fcbbbe5aa956f5ae4..9264539ac121a81a093302b26d302cb2cb406b6a 100644
--- a/Source/devtools/front_end/sdk/InspectorBackend.js
+++ b/Source/devtools/front_end/sdk/InspectorBackend.js
@@ -611,6 +611,7 @@ InspectorBackendClass.MainConnection = function()
 {
     InspectorBackendClass.Connection.call(this);
     InspectorFrontendHost.events.addEventListener(InspectorFrontendHostAPI.Events.DispatchMessage, this._dispatchMessage, this);
+    InspectorFrontendHost.events.addEventListener(InspectorFrontendHostAPI.Events.DispatchMessageChunk, this._dispatchMessageChunk, this);
 }
 
 InspectorBackendClass.MainConnection.prototype = {
@@ -629,7 +630,26 @@ InspectorBackendClass.MainConnection.prototype = {
      */
     _dispatchMessage: function(event)
     {
-        this.dispatch(/** @type {!Object|string} */ (event.data));
+        this.dispatch(/** @type {string} */ (event.data));

[dgozman, 2014/10/15 13:51:38]

event.data could actually be an object (at least in layout tests).

[pfeldman, 2014/10/15 14:06:59]

Which layout tests?

+    },
+
+    /**
+     * @param {!WebInspector.Event} event
+     */
+    _dispatchMessageChunk: function(event)
+    {
+        var messageChunk = /** @type {string} */ (event.data["messageChunk"]);
+        var messageSize = /** @type {number} */ (event.data["messageSize"]);

[alph, 2014/10/15 13:44:58]

Why do you need size? lastChunk boolean should be enough.

[pfeldman, 2014/10/15 14:06:59]

I'm doing it for consistency with the backend. Also total size allows proper
allocation in case we use typed arrays, etc.

+        if (messageSize) {
+            this._messageBuffer = "";
+            this._messageSize = messageSize;
+        }
+        this._messageBuffer += messageChunk;
+        if (this._messageBuffer.length === this._messageSize) {
+            this.dispatch(this._messageBuffer);

[dgozman, 2014/10/15 13:51:38]

It's safer to clear |this._messageBuffer| and |this._messageSize| for the case
of recursive dispatches caused by this call.

[pfeldman, 2014/10/15 14:06:59]

This is an async IPC call, we should not re-enter.

+            this._messageBuffer = "";
+            this._messageSize = 0;
+        }
     },
 
     __proto__: InspectorBackendClass.Connection.prototype