Fix sampling profiler to use thread's cpu clock.

The sampling profiler was using the sampling thread's cpu clock to
measure cpu time, instead of the sampled thread's cpu clock.

Change-Id: Ief1f82e07e0353192c61521f67dec7a761905f64
diff --git a/runtime/thread.h b/runtime/thread.h
index b9b93dd..f16695d 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -267,6 +267,9 @@
   // Sets the thread's name.
   void SetThreadName(const char* name) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
+  // Returns the thread-specific CPU-time clock in microseconds or -1 if unavailable.
+  uint64_t GetCpuMicroTime() const;
+
   mirror::Object* GetPeer() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     CHECK(jpeer_ == NULL);
     return opeer_;