DevTools: Cache the original content on UISourceCode

third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js

 /*
  * Copyright (C) 2011 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 50 matching lines @@
     /** @type {!Multimap<string, !Workspace.UISourceCode.LineMarker>} */
     this._decorations = new Multimap();
 
     /** @type {!Array.<!Workspace.Revision>} */
     this.history = [];
 
     /** @type {!Array<!Workspace.UISourceCode.Message>} */
     this._messages = [];
 
     this._contentLoaded = false;
+    /** @type {?Promise<?string>} */
+    this._originalContentPromise = null;
     /** @type {?string} */
     this._content = null;
     this._forceLoadOnCheckContent = false;
     this._checkingContent = false;
     /** @type {?string} */
     this._lastAcceptedContent = null;
     /** @type {?string} */
     this._workingCopy = null;
     /** @type {?function() : string} */
     this._workingCopyGetter = null;
@@ skipping 201 matching lines @@
   }
 
   forceLoadOnCheckContent() {
     this._forceLoadOnCheckContent = true;
   }
 
   /**
    * @return {!Promise<?string>}
    */
   requestOriginalContent() {
-    var callback;
-    var promise = new Promise(fulfill => callback = fulfill);
-    this._project.requestFileContent(this, callback);
-    return promise;
+    if (this._originalContentPromise)
+      return this._originalContentPromise;
+    var fulfill;
+    this._originalContentPromise = new Promise(x => fulfill = x);
+    this._project.requestFileContent(this, fulfill);
+    return this._originalContentPromise;
   }
 
   /**
    * @param {string} content
    */
   _commitContent(content) {
     if (this._project.canSetFileContent()) {
-      this._project.setFileContent(this, content, function() {});
+      // Cache the original content before we overwrite it.
+      this.requestOriginalContent().then(() => this._project.setFileContent(this, content, function() {}));

[lushnikov, 2016/12/20 01:05:23]

this should be in filesystemworkspacebindings

     } else if (this._url && Workspace.fileManager.isURLSaved(this._url)) {
       Workspace.fileManager.save(this._url, content, false, function() {});
       Workspace.fileManager.close(this._url);
     }
     this._contentCommitted(content, true);
   }
 
   /**
    * @param {string} content
    * @param {boolean} committedByUser
@@ skipping 593 matching lines @@
 Workspace.UISourceCodeMetadata = class {
   /**
    * @param {?Date} modificationTime
    * @param {?number} contentSize
    */
   constructor(modificationTime, contentSize) {
     this.modificationTime = modificationTime;
     this.contentSize = contentSize;
   }
 };