Enable test LayerTreeHostTestBreakSwapPromise with verbose logging information

The log of the flaky LayerTreeHostTestBreakSwapPromise test shows that

[ RUN      ] LayerTreeHostTestBreakSwapPromise.RunMultiThread_DelegatingRenderer_ImplSidePaint
c:\b\build\slave\win_x64_builder\build\src\cc\trees\layer_tree_host_unittest.cc(4500): error: Value of: swap_promise_result_[2].did_not_swap_called
Actual: false
Expected: true
c:\b\build\slave\win_x64_builder\build\src\cc\trees\layer_tree_host_unittest.cc(4501): error: Value of: swap_promise_result_[2].reason
Actual: 0
Expected: SwapPromise::SWAP_FAILS
Which is: 1
[  FAILED  ] LayerTreeHostTestBreakSwapPromise.RunMultiThread_DelegatingRenderer_ImplSidePaint (3 ms)

We have a EXPECT_TRUE on the SwapPromise's dtor to be called which passes.
It means we destroyed the SwapPromise without ever breaking them first
(no DidNotSwap ever called). I checked all the code path where we destroy
SwapPromise and we always break them first. So I can't figure out why it
is the case. I am adding some logging information and turn this test back
on, hopefully next time it fails on the bot I can use the extra logging
information to debug.

BUG=393995

Review URL: https://codereview.chromium.org/477443002

Cr-Commit-Position: refs/heads/master@{#289679}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289679 0039d316-1c4b-4281-b951-d872f2087c98

cc/trees/layer_tree_host_unittest.cc

@@ -4423,11 +4423,19 @@ class TestSwapPromise : public SwapPromise {
 
   virtual ~TestSwapPromise() {
     base::AutoLock lock(result_->lock);
+    LOG(ERROR) << "~TestSwapPromise() "
+               << " did_swap_called " << result_->did_swap_called
+               << " did_not_swap_called " << result_->did_not_swap_called
+               << " result addr " << result_;
     result_->dtor_called = true;
   }
 
   virtual void DidSwap(CompositorFrameMetadata* metadata) OVERRIDE {
     base::AutoLock lock(result_->lock);
+    LOG(ERROR) << "TestSwapPromise::DidSwap "
+               << " did_swap_called " << result_->did_swap_called
+               << " did_not_swap_called " << result_->did_not_swap_called
+               << " result addr " << result_;
     EXPECT_FALSE(result_->did_swap_called);
     EXPECT_FALSE(result_->did_not_swap_called);
     result_->did_swap_called = true;
@@ -4435,6 +4443,11 @@ class TestSwapPromise : public SwapPromise {
 
   virtual void DidNotSwap(DidNotSwapReason reason) OVERRIDE {
     base::AutoLock lock(result_->lock);
+    LOG(ERROR) << "TestSwapPromise::DidNotSwap "
+               << " reason " << reason
+               << " did_swap_called " << result_->did_swap_called
+               << " did_not_swap_called " << result_->did_not_swap_called
+               << " result addr " << result_;
     EXPECT_FALSE(result_->did_swap_called);
     EXPECT_FALSE(result_->did_not_swap_called);
     result_->did_not_swap_called = true;
@@ -4520,7 +4533,8 @@ class LayerTreeHostTestBreakSwapPromise : public LayerTreeHostTest {
 };
 
 // TODO(miletus): Flaky test: crbug.com/393995
-// MULTI_THREAD_TEST_F(LayerTreeHostTestBreakSwapPromise);
+// Enabled with verbose logging information.
+MULTI_THREAD_TEST_F(LayerTreeHostTestBreakSwapPromise);
 
 class LayerTreeHostTestBreakSwapPromiseForVisibilityAbortedCommit
     : public LayerTreeHostTest {