Introduce mojo interface for collecting StackSamplingProfiler data

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 9424ca0081b78d9b4681b7d08ac7521dd71b106b..bf5a4f337219f76b782189fde2c5aa2f9646c640 100644
--- a/base/profiler/stack_sampling_profiler.h
+++ b/base/profiler/stack_sampling_profiler.h
@@ -247,8 +247,10 @@ class BASE_EXPORT StackSamplingProfiler {
   DISALLOW_COPY_AND_ASSIGN(StackSamplingProfiler);
 };
 
-// The metrics provider code wants to put Samples in a map and compare them,
-// which requires us to define a few operators.
+// These operators permit types to be compared and used in a map of Samples, as
+// 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::Frame& a,
                             const StackSamplingProfiler::Frame& b);
 BASE_EXPORT bool operator<(const StackSamplingProfiler::Frame& a,