Use movable types for CallStackProfile(s) to remove copying of 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 bf5a4f337219f76b782189fde2c5aa2f9646c640..228cc5bae3c0b14bb376d79ec45d7a768d29b25c 100644
--- a/base/profiler/stack_sampling_profiler.h
+++ b/base/profiler/stack_sampling_profiler.h
@@ -113,9 +113,13 @@ class BASE_EXPORT StackSamplingProfiler {
   // CallStackProfile represents a set of samples.
   struct BASE_EXPORT CallStackProfile {
     CallStackProfile();
-    CallStackProfile(const CallStackProfile& other);
+    CallStackProfile(CallStackProfile&& other);
     ~CallStackProfile();
 
+    CallStackProfile& operator=(CallStackProfile&& other);
+
+    CallStackProfile CopyForTesting() const;
+
     std::vector<Module> modules;
     std::vector<Sample> samples;
 
@@ -124,6 +128,10 @@ class BASE_EXPORT StackSamplingProfiler {
 
     // Time between samples.
     TimeDelta sampling_period;
+
+   private:
+    // Copying is possible but expensive so disallow it; use std::move instead.

[Mike Wittman, 2016/10/21 18:05:29]

nit: ... disallow it _from outside the class_ ...

[bcwhite, 2016/10/24 13:17:45]

Done.

+    CallStackProfile(const CallStackProfile& other);

[Mike Wittman, 2016/10/21 18:05:29]

should we have DISALLOW_ASSIGN here?

[bcwhite, 2016/10/24 13:17:45]

Done, though I don't think it's necessary because I don't believe the method
will get generated when there is a "move" version that is defined explicitly.

   };
 
   using CallStackProfiles = std::vector<CallStackProfile>;
@@ -151,7 +159,8 @@ class BASE_EXPORT StackSamplingProfiler {
     TimeDelta sampling_interval;
   };
 
-  // The callback type used to collect completed profiles.
+  // The callback type used to collect completed profiles. The passed |profiles|
+  // are move-only.
   //
   // IMPORTANT NOTE: the callback is invoked on a thread the profiler
   // constructs, rather than on the thread used to construct the profiler and
@@ -159,7 +168,7 @@ class BASE_EXPORT StackSamplingProfiler {
   // threads with message loops that create StackSamplingProfilers, posting a
   // task to the message loop with a copy of the profiles is the recommended
   // thread-safe callback implementation.
-  using CompletedCallback = Callback<void(const CallStackProfiles&)>;
+  using CompletedCallback = Callback<void(CallStackProfiles)>;
 
   // Creates a profiler that sends completed profiles to |callback|. The second
   // constructor is for test purposes.