DevTools: Add Closure docs and clean up 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..7872902a8c3287ff3140427ab810e47d36659a70 100644
--- a/third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js
+++ b/third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js
@@ -56,8 +56,6 @@ Workspace.UISourceCode = class extends Common.Object {
     }
 
     this._contentType = contentType;
-    /** @type {?function(?string)} */
-    this._requestContentCallback = null;
     /** @type {?Promise<?string>} */
     this._requestContentPromise = null;
     /** @type {!Multimap<string, !Workspace.UISourceCode.LineMarker>} */
@@ -68,6 +66,18 @@ Workspace.UISourceCode = class extends Common.Object {
 
     /** @type {!Array<!Workspace.UISourceCode.Message>} */
     this._messages = [];
+
+    this._contentLoaded = false;
+    /** @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;
   }
 
   /**
@@ -210,15 +220,21 @@ Workspace.UISourceCode = class extends Common.Object {
    * @return {!Promise<?string>}
    */
   requestContent() {
-    if (this._content || this._contentLoaded)
-      return Promise.resolve(this._content);
-    var promise = this._requestContentPromise;
-    if (!promise) {
-      promise = new Promise(fulfill => this._requestContentCallback = fulfill);
-      this._requestContentPromise = promise;
-      this._project.requestFileContent(this, this._fireContentAvailable.bind(this));
+    if (this._requestContentPromise)
+      return this._requestContentPromise;
+
+    if (this._contentLoaded) {
+      this._requestContentPromise = Promise.resolve(this._content);
+    } else {
+      var fulfill;
+      this._requestContentPromise = new Promise(x => fulfill = x);
+      this._project.requestFileContent(this, content => {
+        this._contentLoaded = true;
+        this._content = content;
+        fulfill(content);
+      });
     }
-    return promise;
+    return this._requestContentPromise;
   }
 
   checkContentUpdated() {
@@ -243,11 +259,11 @@ Workspace.UISourceCode = class extends Common.Object {
         this.setWorkingCopy(workingCopy);
         return;
       }
-      if (typeof this._lastAcceptedContent === 'string' && this._lastAcceptedContent === updatedContent)
+      if (this._lastAcceptedContent === updatedContent)
         return;
 
       if (this._content === updatedContent) {
-        delete this._lastAcceptedContent;
+        this._lastAcceptedContent = null;
         return;
       }
 
@@ -297,9 +313,10 @@ Workspace.UISourceCode = class extends Common.Object {
    * @param {boolean} committedByUser
    */
   _contentCommitted(content, committedByUser) {
-    delete this._lastAcceptedContent;
+    this._lastAcceptedContent = null;
     this._content = content;
     this._contentLoaded = true;
+    this._requestContentPromise = null;
 
     var lastRevision = this.history.length ? this.history[this.history.length - 1] : null;
     if (!lastRevision || lastRevision._content !== this._content) {
@@ -385,11 +402,11 @@ Workspace.UISourceCode = class extends Common.Object {
   workingCopy() {
     if (this._workingCopyGetter) {
       this._workingCopy = this._workingCopyGetter();
-      delete this._workingCopyGetter;
+      this._workingCopyGetter = null;
     }
     if (this.isDirty())
-      return this._workingCopy;
-    return this._content;
+      return /** @type {string} */ (this._workingCopy);
+    return this._content || '';
   }
 
   resetWorkingCopy() {
@@ -398,8 +415,8 @@ Workspace.UISourceCode = class extends Common.Object {
   }
 
   _innerResetWorkingCopy() {
-    delete this._workingCopy;
-    delete this._workingCopyGetter;
+    this._workingCopy = null;
+    this._workingCopyGetter = null;
   }
 
   /**
@@ -407,10 +424,13 @@ Workspace.UISourceCode = class extends Common.Object {
    */
   setWorkingCopy(newWorkingCopy) {
     this._workingCopy = newWorkingCopy;
-    delete this._workingCopyGetter;
+    this._workingCopyGetter = null;
     this._workingCopyChanged();
   }
 
+  /**
+  * @param {function(): string } workingCopyGetter
+  */
   setWorkingCopyGetter(workingCopyGetter) {
     this._workingCopyGetter = workingCopyGetter;
     this._workingCopyChanged();
@@ -427,7 +447,7 @@ Workspace.UISourceCode = class extends Common.Object {
     if (!this._workingCopyGetter)
       return;
     this._workingCopy = this._workingCopyGetter();
-    delete this._workingCopyGetter;
+    this._workingCopyGetter = null;
   }
 
   commitWorkingCopy() {
@@ -439,7 +459,7 @@ Workspace.UISourceCode = class extends Common.Object {
    * @return {boolean}
    */
   isDirty() {
-    return typeof this._workingCopy !== 'undefined' || typeof this._workingCopyGetter !== 'undefined';
+    return this._workingCopy !== null || this._workingCopyGetter !== null;
   }
 
   /**
@@ -482,20 +502,6 @@ Workspace.UISourceCode = class extends Common.Object {
   }
 
   /**
-   * @param {?string} content
-   */
-  _fireContentAvailable(content) {
-    this._contentLoaded = true;
-    this._content = content;
-
-    var callback = this._requestContentCallback;
-    this._requestContentCallback = null;
-    this._requestContentPromise = null;
-
-    callback.call(null, content);
-  }
-
-  /**
    * @return {boolean}
    */
   contentLoaded() {