Add process lifetime annotations to stack samples.

base/profiler/stack_sampling_profiler.h

Index: base/profiler/stack_sampling_profiler.h
diff --git a/base/profiler/stack_sampling_profiler.h b/base/profiler/stack_sampling_profiler.h
index cf1daf7e16d4b1846fa1b20a3c79f0f2578ce100..30ca1f00f542d562d06dec72ceaf224e20e7d6ef 100644
--- a/base/profiler/stack_sampling_profiler.h
+++ b/base/profiler/stack_sampling_profiler.h
@@ -11,6 +11,7 @@
 #include <string>
 #include <vector>
 
+#include "base/atomicops.h"
 #include "base/base_export.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
@@ -64,6 +65,12 @@ class NativeStackSamplerTestDelegate;
 // record those modules associated with the recorded stack frames.
 class BASE_EXPORT StackSamplingProfiler {
  public:
+  // These types are defined simply for clarity in places that define them
+  // (using this as the base type for an enum) and in methods that take them
+  // as parameters.
+  using ProcessPhase = int;
+  using ProcessActivity = int;

[Mike Wittman, 2016/11/02 17:14:39]

Can we avoid defining these typedefs and just use "int" in the interfaces? I
feel like these are a net negative for readability in that they don't add
information to the interfaces below, and they hide the type in use, forcing the
reader to refer back here to be able to fully understand the interfaces.

[bcwhite, 2016/11/02 20:10:45]

I had wanted to clearly define what is being passed.  But now that I've got the
constants generated in the .proto file, it has to be an "int" anyway.

+
   // Module represents the module (DLL or exe) corresponding to a stack frame.
   struct BASE_EXPORT Module {
     Module();
@@ -107,8 +114,28 @@ class BASE_EXPORT StackSamplingProfiler {
     size_t module_index;
   };
 
-  // Sample represents a set of stack frames.
-  using Sample = std::vector<Frame>;
+  // Sample represents a set of stack frames with some extra information.
+  struct BASE_EXPORT Sample {
+    Sample();
+    Sample(const Sample& sample);
+    ~Sample();
+
+    // These constructors are used only during testing.
+    Sample(const Frame& frame);
+    Sample(const std::vector<Frame>& frames);
+
+    // The entire stack frame when the sample is taken.
+    std::vector<Frame> frames;
+
+    // A bit-field indicating which process phases have passed. This can be
+    // used to tell where in the process lifetime the samples are taken. See
+    // ProcessPhase, above.
+    uint32_t process_phases = 0;
+
+    // A bit-field indicating activities which were active when the frame was
+    // captured. See ProcessActivity, above.
+    uint32_t current_activities = 0;
+  };
 
   // CallStackProfile represents a set of samples.
   struct BASE_EXPORT CallStackProfile {
@@ -201,6 +228,12 @@ class BASE_EXPORT StackSamplingProfiler {
   // whichever occurs first.
   void Stop();
 
+  // Set the current system state that is recorded with each captured stack
+  // frame. These are all thread-safe so can be called from anywhere.

[Mike Wittman, 2016/11/02 17:14:39]

Document that the valid values are between 0 and 31.

[bcwhite, 2016/11/02 20:10:45]

Done.

+  static void SetProcessPhase(ProcessPhase phase);
+  static void RecordActivityBegin(ProcessActivity activity);
+  static void RecordActivityEnd(ProcessActivity activity);
+
  private:
   // SamplingThread is a separate thread used to suspend and sample stacks from
   // the target thread.
@@ -243,6 +276,17 @@ class BASE_EXPORT StackSamplingProfiler {
     DISALLOW_COPY_AND_ASSIGN(SamplingThread);
   };
 
+  // Adds "phases" and "activities" annotations to a Sample.
+  static void RecordAnnotations(Sample* sample);
+
+  // These global variables hold current system state. These values are
+  // recorded with every captured sample, done on a separate thread which is
+  // why updates to these must be atomic. A PostTask to move the the updates
+  // to that thread would skew the timing and a lock could result in deadlock
+  // if the thread making a change was also being profiled and got stopped.
+  static subtle::Atomic32 process_phases_;
+  static subtle::Atomic32 current_activities_;
+
   // The thread whose stack will be sampled.
   PlatformThreadId thread_id_;
 
@@ -263,6 +307,12 @@ class BASE_EXPORT StackSamplingProfiler {
 // done in tests and by the metrics provider code.
 BASE_EXPORT bool operator==(const StackSamplingProfiler::Module& a,
                             const StackSamplingProfiler::Module& b);
+BASE_EXPORT bool operator==(const StackSamplingProfiler::Sample& a,
+                            const StackSamplingProfiler::Sample& b);
+BASE_EXPORT bool operator!=(const StackSamplingProfiler::Sample& a,
+                            const StackSamplingProfiler::Sample& b);
+BASE_EXPORT bool operator<(const StackSamplingProfiler::Sample& a,
+                           const StackSamplingProfiler::Sample& b);
 BASE_EXPORT bool operator==(const StackSamplingProfiler::Frame& a,
                             const StackSamplingProfiler::Frame& b);
 BASE_EXPORT bool operator<(const StackSamplingProfiler::Frame& a,