[heap profiler] Reenable sampling profiler on Android.

It has been temporarily disabled within r666174.

BUG=973430

Change-Id: I747e166f1c6dcba478da897d0c661c5bb6cf2371
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1726661Reviewed-by: Mike Wittman <wittman@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682977}

chrome/BUILD.gn

@@ -1874,6 +1874,7 @@ if (is_android) {
       "//chrome/browser/ui",
       "//chrome/child",
       "//chrome/common",
+      "//chrome/common/profiler",
       "//chrome/gpu",
       "//chrome/renderer",
       "//components/gwp_asan/buildflags",

chrome/app/android/chrome_main_delegate_android.cc

@@ -13,6 +13,7 @@
 #include "base/trace_event/trace_event.h"
 #include "chrome/browser/android/chrome_startup_flags.h"
 #include "chrome/browser/android/metrics/uma_utils.h"
+#include "chrome/common/profiler/main_thread_stack_sampling_profiler.h"
 #include "components/policy/core/browser/android/android_combined_policy_provider.h"
 #include "components/safe_browsing/buildflags.h"
 #include "components/startup_metric_utils/browser/startup_metric_utils.h"
@@ -25,17 +26,16 @@
 
 using safe_browsing::SafeBrowsingApiHandler;
 
-
 // ChromeMainDelegateAndroid is created when the library is loaded. It is always
-// done in the process's main Java thread. But for non browser process, e.g.
+// done in the process' main Java thread. But for a non-browser process, e.g.
 // renderer process, it is not the native Chrome's main thread.
-ChromeMainDelegateAndroid::ChromeMainDelegateAndroid() {
-}
-
-ChromeMainDelegateAndroid::~ChromeMainDelegateAndroid() {
-}
+ChromeMainDelegateAndroid::ChromeMainDelegateAndroid() = default;
+ChromeMainDelegateAndroid::~ChromeMainDelegateAndroid() = default;
 
 bool ChromeMainDelegateAndroid::BasicStartupComplete(int* exit_code) {
+  // Start the sampling profiler as early as possible.
+  sampling_profiler_ = std::make_unique<MainThreadStackSamplingProfiler>();
+
 #if BUILDFLAG(SAFE_BROWSING_DB_REMOTE)
   safe_browsing_api_handler_.reset(
       new safe_browsing::SafeBrowsingApiHandlerBridge());

chrome/app/android/chrome_main_delegate_android.h

@@ -12,6 +12,8 @@
 #include "components/safe_browsing/buildflags.h"
 #include "content/public/browser/browser_main_runner.h"
 
+class MainThreadStackSamplingProfiler;
+
 namespace safe_browsing {
 class SafeBrowsingApiHandler;
 }
@@ -32,6 +34,7 @@ class ChromeMainDelegateAndroid : public ChromeMainDelegate {
   void ProcessExiting(const std::string& process_type) override;
 
  private:
+  std::unique_ptr<MainThreadStackSamplingProfiler> sampling_profiler_;
   std::unique_ptr<content::BrowserMainRunner> browser_runner_;
 
 #if BUILDFLAG(SAFE_BROWSING_DB_REMOTE)

chrome/common/thread_profiler.cc

@@ -159,12 +159,8 @@ std::unique_ptr<ThreadProfiler> ThreadProfiler::CreateAndStartOnMainThread() {
 // static
 void ThreadProfiler::SetMainThreadTaskRunner(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
-#if !defined(OS_ANDROID)
-  // TODO(asvitkine): The code path where we create the profiler instance in
-  // chrome_main.cc does not run on Android.
   DCHECK(g_main_thread_instance);
   g_main_thread_instance->SetMainThreadTaskRunnerImpl(task_runner);
-#endif
 }
 
 void ThreadProfiler::SetAuxUnwinderFactory(

chrome/test/BUILD.gn

@@ -5673,6 +5673,7 @@ test("chrome_app_unittests") {
     "//base/test:test_support",
     "//chrome/browser",
     "//chrome/child",
+    "//chrome/common/profiler",
     "//chrome/gpu",
     "//components/crash/core/common",
     "//components/flags_ui:switches",

chrome/test/base/chrome_test_launcher.cc

@@ -200,14 +200,12 @@ int LaunchChromeTests(size_t parallel_jobs,
 
   const auto& command_line = *base::CommandLine::ForCurrentProcess();
 
-#if !defined(OS_ANDROID)
   // Initialize sampling profiler for tests that relaunching a browser. This
   // mimics the behavior in standalone Chrome, where this is done in
   // chrome/app/chrome_main.cc, which does not get called by tests.
   std::unique_ptr<MainThreadStackSamplingProfiler> sampling_profiler;
   if (command_line.HasSwitch(content::kLaunchAsBrowser))
     sampling_profiler = std::make_unique<MainThreadStackSamplingProfiler>();
-#endif
 
 #if defined(OS_LINUX) || defined(OS_ANDROID)
   ChromeCrashReporterClient::Create();

components/metrics/call_stack_profile_builder.cc

@@ -250,12 +250,8 @@ void CallStackProfileBuilder::SetParentProfileCollectorForChildProcess(
 void CallStackProfileBuilder::PassProfilesToMetricsProvider(
     SampledProfile sampled_profile) {
   if (sampled_profile.process() == BROWSER_PROCESS) {
-    // TODO(crbug.com/973430): Remove the check once profile reporting on
-    // Android is sorted out.
-#if !defined(OS_ANDROID)
     GetBrowserProcessReceiverCallbackInstance().Run(profile_start_time_,
                                                     std::move(sampled_profile));
-#endif
   } else {
     g_child_call_stack_profile_collector.Get()
         .ChildCallStackProfileCollector::Collect(profile_start_time_,