Revert "Disabled BackgroundTracingManagerBrowserTest on Android."

This reverts commit 43d39c4b.

Reason for revert: Speculatively re-enable after  https://chromium-review.googlesource.com/c/chromium/src/+/1536801

Original change's description:
> Disabled BackgroundTracingManagerBrowserTest on Android.
> 
> Flaky on Android.
> 
> Bug: 945516
> Change-Id: I9566206394483cb11aebc029321d87f50ace1f29
> Tbr: dsinclair@chromium.org
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1538882
> Reviewed-by: Justin DeWitt <dewittj@chromium.org>
> Commit-Queue: Justin DeWitt <dewittj@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#644052}

TBR=dsinclair@chromium.org,dewittj@chromium.org

Change-Id: I8bd035f487c59500ba9b8dd90e8901f81b2349b7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 945516
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1540297Reviewed-by: oysteine <oysteine@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644465}

content/browser/tracing/background_tracing_manager_browsertest.cc

@@ -17,7 +17,6 @@
 #include "base/strings/pattern.h"
 #include "base/task/post_task.h"
 #include "base/trace_event/trace_event.h"
-#include "build/build_config.h"
 #include "content/browser/tracing/background_startup_tracing_observer.h"
 #include "content/browser/tracing/background_tracing_active_scenario.h"
 #include "content/browser/tracing/background_tracing_manager_impl.h"
@@ -395,14 +394,8 @@ IN_PROC_BROWSER_TEST_F(BackgroundTracingManagerBrowserTest,
 }
 
 // This tests that non-whitelisted args get stripped if required.
-#if defined(OS_ANDROID)
-// Disabled on Android due to flakiness, https://crbug.com/945516 for details.
-#define MAYBE_NotWhitelistedArgsStripped DISABLED_NotWhitelistedArgsStripped
-#else
-#define MAYBE_NotWhitelistedArgsStripped NotWhitelistedArgsStripped
-#endif
 IN_PROC_BROWSER_TEST_F(BackgroundTracingManagerBrowserTest,
-                       MAYBE_NotWhitelistedArgsStripped) {
+                       NotWhitelistedArgsStripped) {
   TestTraceReceiverHelper trace_receiver_helper;
   TestBackgroundTracingHelper background_tracing_helper;