DevTools: [source maps] do not consider missing target files in workspace an error.

Source/devtools/front_end/bindings/CompilerScriptMapping.js

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 131 matching lines @@
             if (this._scriptForSourceMap.get(sourceMap)) {
                 this._sourceMapForScriptId[script.scriptId] = sourceMap;
                 this._debuggerWorkspaceBinding.updateLocations(script);
                 return;
             }
 
             this._sourceMapForScriptId[script.scriptId] = sourceMap;
             this._scriptForSourceMap.set(sourceMap, script);
 
             var sourceURLs = sourceMap.sources();
+            var missingSources = [];
             for (var i = 0; i < sourceURLs.length; ++i) {
                 var sourceURL = sourceURLs[i];
                 if (this._sourceMapForURL.get(sourceURL))
                     continue;
                 this._sourceMapForURL.set(sourceURL, sourceMap);
                 if (!this._workspace.hasMappingForURL(sourceURL) && !this._workspace.uiSourceCodeForURL(sourceURL)) {
                     var contentProvider = sourceMap.sourceContentProvider(sourceURL, WebInspector.resourceTypes.Script);
                     this._networkWorkspaceBinding.addFileForURL(sourceURL, contentProvider, script.isContentScript());
                 }
                 var uiSourceCode = this._workspace.uiSourceCodeForURL(sourceURL);
-                if (uiSourceCode)
+                if (uiSourceCode) {
                     this._bindUISourceCode(uiSourceCode);
-                else
-                    WebInspector.console.error(WebInspector.UIString("Failed to locate workspace file mapped to URL %s from source map %s", sourceURL, sourceMap.url()));
+                } else {
+                    if (missingSources.length < 3)
+                        missingSources.push(sourceURL);
+                    else if (missingSources.peekLast() !== "\u2026")
+                        missingSources.push("\u2026");
+                }
             }
+            if (missingSources.length) {
+                WebInspector.console.warn(
+                    WebInspector.UIString("Source map %s points to the files missing from the workspace: [%s]",
+                                          sourceMap.url(), missingSources.join(", ")));
+            }
+
             this._debuggerWorkspaceBinding.updateLocations(script);
         }
     },
 
     /**
      * @return {boolean}
      */
     isIdentity: function()
     {
         return false;
@@ skipping 120 matching lines @@
         this._sourceMapForScriptId = {};
         this._scriptForSourceMap.clear();
         this._sourceMapForURL.clear();
     },
 
     dispose: function()
     {
         this._workspace.removeEventListener(WebInspector.Workspace.Events.UISourceCodeAdded, this._uiSourceCodeAddedToWorkspace, this);
     }
 }