DevTools: [Sources] Improve editor load time by optimizing setMimeType

third_party/WebKit/Source/devtools/front_end/text_editor/CodeMirrorTextEditor.js

Index: third_party/WebKit/Source/devtools/front_end/text_editor/CodeMirrorTextEditor.js
diff --git a/third_party/WebKit/Source/devtools/front_end/text_editor/CodeMirrorTextEditor.js b/third_party/WebKit/Source/devtools/front_end/text_editor/CodeMirrorTextEditor.js
index 5e1c09dabb21a8da2d9faff18e7d26b7359e010a..fdcc9c507c6d7672ba90f4e9da86c607dce2c3a0 100644
--- a/third_party/WebKit/Source/devtools/front_end/text_editor/CodeMirrorTextEditor.js
+++ b/third_party/WebKit/Source/devtools/front_end/text_editor/CodeMirrorTextEditor.js
@@ -164,6 +164,7 @@ TextEditor.CodeMirrorTextEditor = class extends UI.VBox {
 
     this._needsRefresh = true;
 
+    this._mimeType = '';
     if (options.mimeType)
       this.setMimeType(options.mimeType);
     if (options.autoHeight)
@@ -264,9 +265,9 @@ TextEditor.CodeMirrorTextEditor = class extends UI.VBox {
 
   /**
    * @param {string} mimeType
-   * @return {!Promise}
+   * @param {function()} callback
    */
-  static _loadMimeTypeModes(mimeType) {
+  static _loadMimeTypeModes(mimeType, callback) {

[lushnikov, 2016/11/16 05:23:35]

let's rather split this into two functions. It would be easier to read and
understand

[einbinder, 2016/11/16 23:17:54]

Done.

     var installed = TextEditor.CodeMirrorTextEditor._loadedMimeModeExtensions;
 
     var nameToExtension = new Map();
@@ -292,7 +293,12 @@ TextEditor.CodeMirrorTextEditor = class extends UI.VBox {
     var promises = [];
     for (var extension of modesToLoad)
       promises.push(extension.instance().then(installMode.bind(null, extension)));
-    return Promise.all(promises);
+
+    // If we can, run the callback right away to avoid highlighting twice.
+    if (!promises.length)
+      callback();
+    else
+      Promise.all(promises).then(callback);
 
     /**
      * @param {!Runtime.Extension} extension
@@ -609,15 +615,36 @@ TextEditor.CodeMirrorTextEditor = class extends UI.VBox {
 
   /**
    * @param {string} mimeType
-   * @return {!Promise}
    */
   setMimeType(mimeType) {
-    if (this._hasLongLines())
-      this._enableLongLinesMode();
-    else
-      this._disableLongLinesMode();
-    return TextEditor.CodeMirrorTextEditor._loadMimeTypeModes(mimeType).then(
-        () => this._codeMirror.setOption('mode', mimeType));
+    this._mimeType = mimeType;
+    TextEditor.CodeMirrorTextEditor._loadMimeTypeModes(mimeType, setMode.bind(this));
+
+    /**
+     * @this {TextEditor.CodeMirrorTextEditor}
+     */
+    function setMode() {
+      var rewrittenMimeType = this.rewriteMimeType(mimeType);
+      if (this._codeMirror.options.mode !== rewrittenMimeType)
+        this._codeMirror.setOption('mode', rewrittenMimeType);
+    }
+  }
+
+  /**
+   * @protected
+   * @param {string} mimeType
+   */
+  rewriteMimeType(mimeType) {
+    // Overridden in SourcesTextEditor
+    return mimeType;
+  }
+
+  /**
+   * @protected
+   * @return {string}
+   */
+  mimeType() {
+    return this._mimeType;
   }
 
   /**
@@ -1077,6 +1104,11 @@ TextEditor.CodeMirrorTextEditor = class extends UI.VBox {
       this._shouldClearHistory = false;
     }
     this._detectLineSeparator(text);
+
+    if (this._hasLongLines())
+      this._enableLongLinesMode();
+    else
+      this._disableLongLinesMode();
   }
 
   /**