DevTools: Fix test inspector-protocol/stylesheet-tracking-restart.html flakiness

The flakiness is caused by unpredictable order of stylesheets binding in InspectorCSSAgent.
This patch replaces HashSet with Vector to make sure the order is maintained.

R=lushnikov

Review URL: https://codereview.chromium.org/339133002

git-svn-id: svn://svn.chromium.org/blink/trunk@176301 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/TestExpectations

@@ -1122,9 +1122,6 @@ crbug.com/384566 svg/custom/textPath-change-reference2.svg [ ImageOnlyFailure Pa
 
 crbug.com/384396 [ Win ] battery-status/page-visibility.html [ Pass Failure Timeout ]
 
-# Made substantially flakier in r176213
-crbug.com/354447 inspector-protocol/stylesheet-tracking-restart.html [ Pass Failure Timeout ]
-
 Bug(eae) fast/text/justify-ideograph-complex.html [ NeedsRebaseline ]
 Bug(eae) fast/text/justify-ideograph-simple.html [ NeedsRebaseline ]
 Bug(eae) media/track/track-cue-rendering-vertical.html [ NeedsRebaseline ]

third_party/WebKit/Source/core/inspector/InspectorCSSAgent.cpp

@@ -517,16 +517,15 @@ void InspectorCSSAgent::setActiveStyleSheets(Document* document, const Vector<CS
     }
 
     HashSet<CSSStyleSheet*> removedSheets(*documentCSSStyleSheets);
-
-    HashSet<CSSStyleSheet*> addedSheets;
+    Vector<CSSStyleSheet*> addedSheets;
     for (Vector<CSSStyleSheet*>::const_iterator it = allSheetsVector.begin(); it != allSheetsVector.end(); ++it) {
         CSSStyleSheet* cssStyleSheet = *it;
         if (removedSheets.contains(cssStyleSheet)) {
             removedSheets.remove(cssStyleSheet);
             if (isInitialFrontendLoad)
-                addedSheets.add(cssStyleSheet);
+                addedSheets.append(cssStyleSheet);
         } else {
-            addedSheets.add(cssStyleSheet);
+            addedSheets.append(cssStyleSheet);
         }
     }
 
@@ -543,7 +542,7 @@ void InspectorCSSAgent::setActiveStyleSheets(Document* document, const Vector<CS
         }
     }
 
-    for (HashSet<CSSStyleSheet*>::iterator it = addedSheets.begin(); it != addedSheets.end(); ++it) {
+    for (Vector<CSSStyleSheet*>::iterator it = addedSheets.begin(); it != addedSheets.end(); ++it) {
         CSSStyleSheet* cssStyleSheet = *it;
         bool isNew = isInitialFrontendLoad || !m_cssStyleSheetToInspectorStyleSheet.contains(cssStyleSheet);
         if (isNew) {