Revert "[DevTools] Make log agent optional."

This reverts commit d0125b8f.

Reason:
Warnings from ServiceWorkerGlobalScope doesn't show up in devtools' console

BUG=594160
TBR=eostroukhov, pfeldman

Review-Url: https://codereview.chromium.org/2344813002
Cr-Commit-Position: refs/heads/master@{#418793}

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

@@ -32,9 +32,8 @@
  * @constructor
  * @extends {WebInspector.SDKModel}
  * @param {!WebInspector.Target} target
- * @param {?Protocol.LogAgent} logAgent
  */
-WebInspector.ConsoleModel = function(target, logAgent)
+WebInspector.ConsoleModel = function(target)
 {
     WebInspector.SDKModel.call(this, WebInspector.ConsoleModel, target);
 
@@ -45,11 +44,9 @@ WebInspector.ConsoleModel = function(target, logAgent)
     this._warnings = 0;
     this._errors = 0;
     this._revokedErrors = 0;
-    this._logAgent = logAgent;
-    if (this._logAgent) {
+    this._logAgent = target.logAgent();
     target.registerLogDispatcher(new WebInspector.LogDispatcher(this));
     this._logAgent.enable();
-    }
 }
 
 /** @enum {symbol} */
@@ -137,7 +134,7 @@ WebInspector.ConsoleModel.prototype = {
 
     requestClearMessages: function()
     {
-        this._logAgent && this._logAgent.clear();
+        this._logAgent.clear();
         this.clear();
     },
 

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

@@ -190,10 +190,8 @@ WebInspector.TargetManager.prototype = {
     {
         var target = new WebInspector.Target(this, name, capabilitiesMask, connection, parentTarget);
 
-        var logAgent = target.hasBrowserCapability() ? target.logAgent() : null;
-
         /** @type {!WebInspector.ConsoleModel} */
-        target.consoleModel = new WebInspector.ConsoleModel(target, logAgent);
+        target.consoleModel = new WebInspector.ConsoleModel(target);
         /** @type {!WebInspector.RuntimeModel} */
         target.runtimeModel = new WebInspector.RuntimeModel(target);