DevTools: update repeat count only when element is requested

third_party/WebKit/Source/devtools/front_end/console/ConsoleViewMessage.js

Index: third_party/WebKit/Source/devtools/front_end/console/ConsoleViewMessage.js
diff --git a/third_party/WebKit/Source/devtools/front_end/console/ConsoleViewMessage.js b/third_party/WebKit/Source/devtools/front_end/console/ConsoleViewMessage.js
index 13e3af830b030d1189e5dee9cbe1d2d0fb148c50..7ec7effb7347488b35b4f7759666b009ca3aa61d 100644
--- a/third_party/WebKit/Source/devtools/front_end/console/ConsoleViewMessage.js
+++ b/third_party/WebKit/Source/devtools/front_end/console/ConsoleViewMessage.js
@@ -122,9 +122,6 @@ Console.ConsoleViewMessage = class {
       iconType = 'smallicon-command-result';
     this._decorationWrapper.appendChild(UI.Icon.create(iconType, 'message-level-icon'));
 
-    // Timestamps may affect repeat counter.
-    this._updateRepeatCountElement();

[pfeldman, 2017/02/21 19:21:12]

I'd rather do it the other way around and create it every time here as you do
with other elements.

[luoe, 2017/02/23 01:09:34]

I tried placing message.updateMessageElement() inside
ConsoleView._tryToCollapseMessages right after the call to
viewMessage.incrementRepeatCount().  Running `for (var
i=0;i<1000;i++){console.error(3);}` takes ~1.8x as long.

Time spent doing layout is about the same, (0.4ms), but the time spent
recalculating style jumps (from 0.05ms to 0.4ms)!

-
     /**
      * @param {number} timestamp
      * @param {boolean} full
@@ -955,11 +952,17 @@ Console.ConsoleViewMessage = class {
    * @return {!Element}
    */
   toMessageElement() {
-    if (this._element)
-      return this._element;
+    if (!this._element) {
+      this._element = createElement('div');
+      this.updateMessageElement();
+    }
+
+    // Update repeat count.
+    var show = this._repeatCount > 1;
+    this._repeatCountElement.textContent = show ? this._repeatCount : '';
+    this._repeatCountElement.classList.toggle('hidden', !show);
+    this._element.classList.toggle('repeated-message', show);
 
-    this._element = createElement('div');
-    this.updateMessageElement();
     return this._element;
   }
 
@@ -1029,22 +1032,10 @@ Console.ConsoleViewMessage = class {
 
   resetIncrementRepeatCount() {
     this._repeatCount = 1;
-    this._updateRepeatCountElement();
   }
 
   incrementRepeatCount() {
     this._repeatCount++;
-    this._updateRepeatCountElement();
-  }
-
-  _updateRepeatCountElement() {
-    if (!this._repeatCountElement)
-      return;
-    var show = this._repeatCount > 1;
-    this._repeatCountElement.textContent = show ? this._repeatCount : '';
-    this._repeatCountElement.classList.toggle('hidden', !show);
-    if (this._element)
-      this._element.classList.toggle('repeated-message', show);
   }
 
   get text() {