Add asserts for shared mutex.

src/core/SkSharedMutex.h

Index: src/core/SkSharedMutex.h
diff --git a/src/core/SkSharedMutex.h b/src/core/SkSharedMutex.h
index a3535dca430aad26b26ab33dc5ef4018609e96df..527bae2b6857f6ed392be27feca48af18fb0be0d 100644
--- a/src/core/SkSharedMutex.h
+++ b/src/core/SkSharedMutex.h
@@ -28,12 +28,18 @@ public:
     // Release lock for exclusive use.
     void release();
 
+    // Fail if exclusive is not held.
+    void assertHeld() const;

[mtklein, 2015/08/19 19:00:51]

Let's do something like this to make sure these are totally no-ops in release.

#ifdef SK_DEBUG
  void assertHeld() const;
  void assertHeldShared() const;
#else
  void assertHeld() const {}
  void assertHeldShared() const {}
#endif

[herb_g, 2015/08/19 20:30:50]

Done.

+
     // Acquire lock for shared use.
     void acquireShared();
 
     // Release lock for shared use.
     void releaseShared();
 
+    // Fail if shared lock not held.
+    void assertHeldShared() const;
+
 private:
     SkAtomic<int32_t> fQueueCounts;
     SkSemaphore fSharedQueue;