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 {?Promise<?string>} */
     this._requestContentPromise = null;
     /** @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 {?string} */
+    this._originalContent = null;
+    /** @type {?string} */
+    this._content = null;
   }
 
   /**
    * @return {!Promise<?Workspace.UISourceCodeMetadata>}
    */
   requestMetadata() {
     return this._project.requestMetadata(this);
   }
 
   /**
@@ skipping 185 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._contentLoaded)
+      return Promise.resolve(this._originalContent);
+    return this.requestContent();
   }
 
   /**
    * @param {string} content
    */
   _commitContent(content) {
     if (this._project.canSetFileContent()) {
       this._project.setFileContent(this, content, function() {});
     } 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
    */
   _contentCommitted(content, committedByUser) {
     delete this._lastAcceptedContent;
-    this._content = content;
-    this._contentLoaded = true;
+    this._setContent(content);

[lushnikov, 2016/12/17 00:10:51]

why do you want to link original content to the content?

Can we make requestOriginalContent() consistently return the same result over
time?

[einbinder, 2016/12/20 00:56:55]

Yep. Done.

 
     var lastRevision = this.history.length ? this.history[this.history.length - 1] : null;
     if (!lastRevision || lastRevision._content !== this._content) {
       var revision = new Workspace.Revision(this, this._content, new Date());
       this.history.push(revision);
     }
 
     this._innerResetWorkingCopy();
     this.dispatchEventToListeners(
         Workspace.UISourceCode.Events.WorkingCopyCommitted, {uiSourceCode: this, content: content});
@@ skipping 69 matching lines @@
   /**
    * @return {string}
    */
   workingCopy() {
     if (this._workingCopyGetter) {
       this._workingCopy = this._workingCopyGetter();
       delete this._workingCopyGetter;
     }
     if (this.isDirty())
       return this._workingCopy;
-    return this._content;
+    return this._content || '';

[einbinder, 2016/12/16 23:43:00]

This could have returned null before.

   }
 
   resetWorkingCopy() {
     this._innerResetWorkingCopy();
     this._workingCopyChanged();
   }
 
   _innerResetWorkingCopy() {
     delete this._workingCopy;
     delete this._workingCopyGetter;
@@ skipping 75 matching lines @@
      */
     function doSearch(content) {
       callback(Common.ContentProvider.performSearchInContent(content, query, caseSensitive, isRegex));
     }
   }
 
   /**
    * @param {?string} content
    */
   _fireContentAvailable(content) {
-    this._contentLoaded = true;
-    this._content = content;
+    this._setContent(content);
 
     var callback = this._requestContentCallback;
     this._requestContentCallback = null;
     this._requestContentPromise = null;
 
     callback.call(null, content);
   }
 
   /**
+   * @param {?string} content
+   */
+  _setContent(content) {
+    if (!this._contentLoaded)
+      this._originalContent = content;
+    this._contentLoaded = true;
+    this._content = content;
+  }
+
+  /**
    * @return {boolean}
    */
   contentLoaded() {
     return this._contentLoaded;
   }
 
   /**
    * @param {number} lineNumber
    * @param {number=} columnNumber
    * @return {!Workspace.UILocation}
@@ skipping 392 matching lines @@
 Workspace.UISourceCodeMetadata = class {
   /**
    * @param {?Date} modificationTime
    * @param {?number} contentSize
    */
   constructor(modificationTime, contentSize) {
     this.modificationTime = modificationTime;
     this.contentSize = contentSize;
   }
 };