Insist on a Blink GC on RenderViewImpl unit test teardowns.

content/renderer/render_view_browsertest.cc

Index: content/renderer/render_view_browsertest.cc
diff --git a/content/renderer/render_view_browsertest.cc b/content/renderer/render_view_browsertest.cc
index 8c98001097f0fe4f63a7dd455a90d75f89ba046c..868be6fa4836a755b62721625000590bc6a90d60 100644
--- a/content/renderer/render_view_browsertest.cc
+++ b/content/renderer/render_view_browsertest.cc
@@ -59,6 +59,7 @@
 #include "third_party/WebKit/public/platform/WebURLResponse.h"
 #include "third_party/WebKit/public/web/WebDataSource.h"
 #include "third_party/WebKit/public/web/WebDeviceEmulationParams.h"
+#include "third_party/WebKit/public/web/WebHeap.h"
 #include "third_party/WebKit/public/web/WebHistoryCommitType.h"
 #include "third_party/WebKit/public/web/WebHistoryItem.h"
 #include "third_party/WebKit/public/web/WebLocalFrame.h"
@@ -87,6 +88,7 @@
 #include "url/url_constants.h"
 
 using blink::WebFrame;
+using blink::WebHeap;
 using blink::WebInputEvent;
 using blink::WebLocalFrame;
 using blink::WebMouseEvent;
@@ -171,6 +173,13 @@ class RenderViewImplTest : public RenderViewTest {
     RenderViewTest::SetUp();
   }
 
+  // To avoid flaky leak reports, insist on GCing
+  // Blink upon shutdown to clear out garbage.
+  void TearDown() override {
+    WebHeap::collectGarbageForTesting();

[haraken, 2016/01/24 09:27:56]

collectAllGarbageForTesting would be better.

[sof, 2016/01/24 12:35:18]

That's what I thought would be tidier too, but forcing a (conservative) GC is
vital here (and sufficient for these tests.)

*AllGarbageForTesting()'s posting of tasks to run precise GCs along with
processing pending messages afterwards isn't a strong enough guarantee -- you
can still observe flaky leak reports when doing that.

So I will keep it like this.

+    RenderViewTest::TearDown();
+  }
+
   RenderViewImpl* view() {
     return static_cast<RenderViewImpl*>(view_);
   }
@@ -501,7 +510,6 @@ TEST_F(RenderViewImplTest, OnNavStateChanged) {
     EXPECT_TRUE(render_thread_->sink().GetUniqueMessageMatching(
         ViewHostMsg_UpdateState::ID));
   }
-  ProcessPendingMessages();
 }
 
 TEST_F(RenderViewImplTest, OnNavigationHttpPost) {