Revert of Fix leaks in exensions_unittests after enabling Oilpan (patchset #1...

Revert of Fix leaks in exensions_unittests after enabling Oilpan (patchset #1 id:1 of https://codereview.chromium.org/1632763003/ )

Reason for revert:
This CL didn't fix the leak. Also per the discussion in https://codereview.chromium.org/1632763003/, suppressing the leak looks like a reasonable solution at the moment. So revert this CL.

Original issue's description:
> Fix leaks in exensions_unittests after enabling Oilpan
>
> This CL adds an Oilpan's GC before tearing down the extensions_unittests.
>
> BUG=581092
>
> Committed: https://crrev.com/6ae6611de742bb291305a1df558e710213556fa4
> Cr-Commit-Position: refs/heads/master@{#371408}

TBR=rockot@chromium.org,oilpan-reviews@chromium.org,oshima@chromium.org,sigbjornf@opera.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=581092

Review URL: https://codereview.chromium.org/1637013002

Cr-Commit-Position: refs/heads/master@{#371502}

extensions/renderer/module_system_test.cc

@@ -22,7 +22,6 @@
 #include "extensions/renderer/object_backed_native_handler.h"
 #include "extensions/renderer/safe_builtins.h"
 #include "extensions/renderer/utils_native_handler.h"
-#include "third_party/WebKit/public/web/WebHeap.h"
 #include "ui/base/resource/resource_bundle.h"
 
 namespace extensions {
@@ -241,7 +240,6 @@ void ModuleSystemTest::TearDown() {
     old_heap_size = stats.used_heap_size();
     isolate_->RequestGarbageCollectionForTesting(
         v8::Isolate::kFullGarbageCollection);
-    blink::WebHeap::collectAllGarbageForTesting();
     isolate_->GetHeapStatistics(&stats);
   }
 }

tools/valgrind/memcheck/suppressions.txt

@@ -3457,3 +3457,31 @@
    fun:_ZN5blink11WebViewImpl12setMainFrameEPNS_8WebFrameE
    fun:_ZN10extensions14ScopedWebFrameC1Ev
 }
+{
+   bug_581092_a
+   Memcheck:Leak
+   ...
+   fun:_ZN5blink15ContextFeatures13defaultSwitchEv
+   fun:_ZN5blink8DocumentC2ERKNS_12DocumentInitEh
+   fun:_ZN5blink12HTMLDocumentC1ERKNS_12DocumentInitEh
+   fun:_ZN5blink12HTMLDocument6createERKNS_12DocumentInitE
+   fun:_ZN5blink17DOMImplementation14createDocumentERKN3WTF6StringERKNS_12DocumentInitEb
+   fun:_ZN5blink14LocalDOMWindow14createDocumentERKN3WTF6StringERKNS_12DocumentInitEb
+   fun:_ZN5blink14LocalDOMWindow18installNewDocumentERKN3WTF6StringERKNS_12DocumentInitEb
+   fun:_ZN5blink14DocumentLoader15createWriterForEPKNS_*
+}
+{
+   bug_581092_b
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN5blink26RefCountedGarbageCollectedINS_15StyleFilterDataEE13makeKeepAliveEv
+   fun:_ZN5blink26RefCountedGarbageCollectedINS_15StyleFilterDataEE3refEv
+   ...
+   fun:_ZN5blink7DataRefINS_15StyleFilterDataEE4initEv
+   ...
+   fun:_ZN5blink13ComputedStyle6createEv
+   fun:_ZN5blink13StyleResolver16styleForDocumentERNS_8DocumentE
+   fun:_ZN5blink8Document6attachERKNS_4Node13AttachContextE
+   fun:_ZN5blink14LocalDOMWindow18installNewDocumentERKN3WTF6StringERKNS_12DocumentInitEb
+   fun:_ZN5blink14DocumentLoader15createWriterForEPKNS_*
+}