DevTools: avoid slowdown from unnecessary DOM, style mutations on CodeMirrorTextEditor

third_party/WebKit/Source/devtools/front_end/source_frame/UISourceCodeFrame.js

Index: third_party/WebKit/Source/devtools/front_end/source_frame/UISourceCodeFrame.js
diff --git a/third_party/WebKit/Source/devtools/front_end/source_frame/UISourceCodeFrame.js b/third_party/WebKit/Source/devtools/front_end/source_frame/UISourceCodeFrame.js
index 6e013ce940864d0072e5d656289fc7d6db19f0cd..b4233756341115d8e4332e2cbeddd42894af47cb 100644
--- a/third_party/WebKit/Source/devtools/front_end/source_frame/UISourceCodeFrame.js
+++ b/third_party/WebKit/Source/devtools/front_end/source_frame/UISourceCodeFrame.js
@@ -575,6 +575,7 @@ SourceFrame.UISourceCodeFrame.RowMessageBucket = class {
     this._messages = [];
 
     this._level = null;
+    this._throttler = new Common.Throttler(50);
   }
 
   /**
@@ -637,7 +638,10 @@ SourceFrame.UISourceCodeFrame.RowMessageBucket = class {
 
     var rowMessage = new SourceFrame.UISourceCodeFrame.RowMessage(message);
     this._messages.push(rowMessage);
-    this._updateDecoration();
+    this._throttler.schedule(() => {
+      this._updateDecoration();
+      return Promise.resolve();
+    });
   }
 
   /**
@@ -651,7 +655,10 @@ SourceFrame.UISourceCodeFrame.RowMessageBucket = class {
       rowMessage.setRepeatCount(rowMessage.repeatCount() - 1);
       if (!rowMessage.repeatCount())
         this._messages.splice(i, 1);
-      this._updateDecoration();
+      this._throttler.schedule(() => {
+        this._updateDecoration();
+        return Promise.resolve();
+      });
       return;
     }
   }