Reland "[sampling heap profiler] Support stack collection on Android"

This reverts commit db0cac4e.

Reason for revert: The revert didn't affect anything, so re-landing.

Original change's description:
> Revert "[sampling heap profiler] Support stack collection on Android"
> 
> This reverts commit 52601a56.
> 
> Reason for revert: Speculatively reverting to see if this is confusing crashpad on the Mac somehow. See crbug.com/862466.
> 
> Original change's description:
> > [sampling heap profiler] Support stack collection on Android
> > 
> > BUG=803276
> > 
> > Change-Id: I60d7925104b8614aa68c135d52f6089a76675d22
> > Reviewed-on: https://chromium-review.googlesource.com/1128630
> > Reviewed-by: Siddhartha S <ssid@chromium.org>
> > Commit-Queue: Alexei Filippov <alph@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#573880}
> 
> TBR=alph@chromium.org,ssid@chromium.org
> 
> Change-Id: Ie7b4f8b20cd5526420ef836d3a21dda27d4090bb
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 803276
> Reviewed-on: https://chromium-review.googlesource.com/1132357
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>
> Commit-Queue: Dirk Pranke <dpranke@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#574032}

TBR=dpranke@chromium.org,alph@chromium.org,ssid@chromium.org

Change-Id: I41392b0836e75c25ae6b0b9aa243daeef95b6ee7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 803276
Reviewed-on: https://chromium-review.googlesource.com/1134142Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574379}

base/sampling_heap_profiler/sampling_heap_profiler.cc

@@ -21,6 +21,11 @@
 #include "base/threading/thread_local_storage.h"
 #include "build/build_config.h"
 
+#if defined(OS_ANDROID) && BUILDFLAG(CAN_UNWIND_WITH_CFI_TABLE) && \
+    defined(OFFICIAL_BUILD)
+#include "base/trace_event/cfi_backtrace_android.h"
+#endif
+
 namespace base {
 
 using base::allocator::AllocatorDispatch;
@@ -231,6 +236,14 @@ void SamplingHeapProfiler::SetHooksInstallCallback(
 }
 
 uint32_t SamplingHeapProfiler::Start() {
+#if defined(OS_ANDROID) && BUILDFLAG(CAN_UNWIND_WITH_CFI_TABLE) && \
+    defined(OFFICIAL_BUILD)
+  if (!base::trace_event::CFIBacktraceAndroid::GetInitializedInstance()
+           ->can_unwind_stack_frames()) {
+    LOG(WARNING) << "Sampling heap profiler: Stack unwinding is not available.";
+    return 0;
+  }
+#endif
   InstallAllocatorHooksOnce();
   base::subtle::Barrier_AtomicIncrement(&g_running, 1);
   return last_sample_ordinal_;
@@ -309,16 +322,31 @@ void SamplingHeapProfiler::RecordAlloc(void* address,
 void SamplingHeapProfiler::RecordStackTrace(Sample* sample,
                                             uint32_t skip_frames) {
 #if !defined(OS_NACL)
-  // TODO(alph): Consider using debug::TraceStackFramePointers. It should be
-  // somewhat faster than base::debug::StackTrace.
-  base::debug::StackTrace trace;
-  size_t count;
-  void* const* addresses = const_cast<void* const*>(trace.Addresses(&count));
-  const uint32_t kSkipProfilerOwnFrames = 2;
+  constexpr uint32_t kMaxStackEntries = 256;
+  constexpr uint32_t kSkipProfilerOwnFrames = 2;
   skip_frames += kSkipProfilerOwnFrames;
+#if defined(OS_ANDROID) && BUILDFLAG(CAN_UNWIND_WITH_CFI_TABLE) && \
+    defined(OFFICIAL_BUILD)
+  const void* frames[kMaxStackEntries];
+  size_t frame_count =
+      base::trace_event::CFIBacktraceAndroid::GetInitializedInstance()->Unwind(
+          frames, kMaxStackEntries);
+#elif BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
+  const void* frames[kMaxStackEntries];
+  size_t frame_count = base::debug::TraceStackFramePointers(
+      frames, kMaxStackEntries, skip_frames);
+  skip_frames = 0;
+#else
+  // Fall-back to capturing the stack with base::debug::StackTrace,
+  // which is likely slower, but more reliable.
+  base::debug::StackTrace stack_trace(kMaxStackEntries);
+  size_t frame_count = 0;
+  const void* const* frames = stack_trace.Addresses(&frame_count);
+#endif
+
   sample->stack.insert(
-      sample->stack.end(), &addresses[skip_frames],
-      &addresses[std::max(count, static_cast<size_t>(skip_frames))]);
+      sample->stack.end(), const_cast<void**>(&frames[skip_frames]),
+      const_cast<void**>(&frames[std::max<size_t>(frame_count, skip_frames)]));
 #endif
 }
 

base/sampling_heap_profiler/sampling_heap_profiler.h

@@ -105,7 +105,7 @@ class BASE_EXPORT SamplingHeapProfiler {
   std::stack<std::unique_ptr<LockFreeAddressHashSet>> sampled_addresses_stack_;
   std::unordered_map<void*, Sample> samples_;
   std::vector<SamplesObserver*> observers_;
-  uint32_t last_sample_ordinal_ = 0;
+  uint32_t last_sample_ordinal_ = 1;
 
   static SamplingHeapProfiler* instance_;