[oom] Add debug logs to EXPECT to root-cause flakes

After looking through the code, it seems the only thing that could
be going wrong here is |app_state| not thinking we have running
activities during the unit test.

This CL will let us figure out if app_state is the member at fault here,
and hopefully what to do about it.

Bug: 819592
Change-Id: I3f43b3b7ec5dab8c7c5e6ca0b4fa9f2967e4ea9f
Reviewed-on: https://chromium-review.googlesource.com/958190Reviewed-by: Siddhartha S <ssid@chromium.org>
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542621}

chrome/browser/metrics/oom/out_of_memory_reporter_unittest.cc

@@ -55,21 +55,22 @@ class CrashDumpWaiter : public breakpad::CrashDumpManager::Observer {
 
   // Waits for the crash dump notification and returns whether the crash was
   // considered a foreground oom.
-  bool Wait() {
+  const breakpad::CrashDumpManager::CrashDumpDetails& Wait() {
     waiter_.Run();
-    return last_crash_was_oom_.value();
+    return last_crash_details_.value();
   }
 
  private:
   // CrashDumpManager::Observer:
   void OnCrashDumpProcessed(
       const breakpad::CrashDumpManager::CrashDumpDetails& details) override {
-    last_crash_was_oom_ = breakpad::CrashDumpManager::IsForegroundOom(details);
+    last_crash_details_ = details;
     waiter_.Quit();
   }
 
   base::RunLoop waiter_;
-  base::Optional<bool> last_crash_was_oom_;
+  base::Optional<breakpad::CrashDumpManager::CrashDumpDetails>
+      last_crash_details_;
   DISALLOW_COPY_AND_ASSIGN(CrashDumpWaiter);
 };
 #endif  // defined(OS_ANDROID)
@@ -139,8 +140,13 @@ class OutOfMemoryReporterTest : public ChromeRenderViewHostTestHarness,
 #if defined(OS_ANDROID)
     CrashDumpWaiter crash_waiter;
     std::move(crash_closure).Run();
-    bool was_oom = crash_waiter.Wait();
-    EXPECT_EQ(expect_oom, was_oom);
+    const breakpad::CrashDumpManager::CrashDumpDetails& details =
+        crash_waiter.Wait();
+    EXPECT_EQ(expect_oom, breakpad::CrashDumpManager::IsForegroundOom(details))
+        << "process_type: " << details.process_type
+        << " termination_status: " << details.termination_status
+        << " file_size: " << details.file_size
+        << " app_state: " << details.app_state;
 
     // Since the observer list is not ordered, it isn't guaranteed that the
     // OutOfMemoryReporter will be notified at this point. Flush the current