DevTools: Cache the original content on UISourceCode

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

Index: third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js
diff --git a/third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js b/third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js
index 0979e6e0b301302803df054450025f58d676a19e..76aedc8c4e49b386b8f243f53209c42f59cd33c4 100644
--- a/third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js
+++ b/third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js
@@ -68,6 +68,12 @@ Workspace.UISourceCode = class extends Common.Object {
 
     /** @type {!Array<!Workspace.UISourceCode.Message>} */
     this._messages = [];
+
+    this._contentLoaded = false;
+    /** @type {?string} */
+    this._originalContent = null;
+    /** @type {?string} */
+    this._content = null;
   }
 
   /**
@@ -273,10 +279,9 @@ Workspace.UISourceCode = class extends Common.Object {
    * @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();
   }
 
   /**
@@ -298,8 +303,7 @@ Workspace.UISourceCode = class extends Common.Object {
    */
   _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) {
@@ -389,7 +393,7 @@ Workspace.UISourceCode = class extends Common.Object {
     }
     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() {
@@ -485,8 +489,7 @@ Workspace.UISourceCode = class extends Common.Object {
    * @param {?string} content
    */
   _fireContentAvailable(content) {
-    this._contentLoaded = true;
-    this._content = content;
+    this._setContent(content);
 
     var callback = this._requestContentCallback;
     this._requestContentCallback = null;
@@ -496,6 +499,16 @@ Workspace.UISourceCode = class extends Common.Object {
   }
 
   /**
+   * @param {?string} content
+   */
+  _setContent(content) {
+    if (!this._contentLoaded)
+      this._originalContent = content;
+    this._contentLoaded = true;
+    this._content = content;
+  }
+
+  /**
    * @return {boolean}
    */
   contentLoaded() {