The background parser doesn't need to block Virtual Time anymore

For determinism Virtual Time needed to be blocked when the background
parser was running on the background thread.  That thread no longer
exists (it now runs on the main thread) so we can remove the
WebScopedVirtualTimePauser.

Bug: 777763
Change-Id: I0c5f31fcb8c7dbd45ac922be831951143f1c48a9
Reviewed-on: https://chromium-review.googlesource.com/817747
Commit-Queue: Alex Clarke <alexclarke@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523085}

third_party/WebKit/Source/core/html/parser/HTMLDocumentParser.cpp

@@ -797,15 +797,6 @@ void HTMLDocumentParser::StartBackgroundParser() {
   DCHECK(GetDocument());
   have_background_parser_ = true;
 
-  if (GetDocument()->GetFrame() &&
-      GetDocument()->GetFrame()->FrameScheduler()) {
-    virtual_time_pauser_ = GetDocument()
-                               ->GetFrame()
-                               ->FrameScheduler()
-                               ->CreateWebScopedVirtualTimePauser();
-    virtual_time_pauser_.PauseVirtualTime(true);
-  }
-
   // Make sure that a resolver is set up, so that the correct viewport
   // dimensions will be fed to the background parser and preload scanner.
   if (GetDocument()->Loader())
@@ -856,7 +847,6 @@ void HTMLDocumentParser::StopBackgroundParser() {
   DCHECK(ShouldUseThreading());
   DCHECK(have_background_parser_);
 
-  virtual_time_pauser_.PauseVirtualTime(false);
   have_background_parser_ = false;
 
   // Make this sync, as lsan triggers on some unittests if the task runner is

third_party/WebKit/Source/core/html/parser/HTMLDocumentParser.h

@@ -285,8 +285,6 @@ class CORE_EXPORT HTMLDocumentParser : public ScriptableDocumentParser,
   bool tried_loading_link_headers_;
   bool added_pending_stylesheet_in_body_;
   bool is_waiting_for_stylesheets_;
-
-  WebScopedVirtualTimePauser virtual_time_pauser_;
 };
 
 }  // namespace blink