Create debug only SkSingleOwner

include/private/SkMutex.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkMutex_DEFINED
 #define SkMutex_DEFINED
 
@@ skipping 36 matching lines @@
     }
 
     void assertHeld() {
         SkASSERT(fOwner == SkGetThreadID());
     }
 
     SkBaseSemaphore fSemaphore;
     SkDEBUGCODE(SkThreadID fOwner;)
 };
 
+#ifdef SK_DEBUG
+// This is a slow recursive mutex for debug purposes only
+struct SkRecursiveMutex {
+    SkRecursiveMutex () {
+        fSemaphore = SK_MUTEX_SEMAPHORE_INIT;
+        fOwner = kIllegalThreadID;
+        fAcquireCount = 0;
+    }
+    ~SkRecursiveMutex () { fSemaphore.deleteSemaphore(); }
+
+    void acquire() {
+        if (fOwner != SkGetThreadID()) {
+            fSemaphore.wait();
+        }
+        fAcquireCount++;
+        fOwner = SkGetThreadID();
+    }
+
+    void release() {
+        this->assertHeld();
+        if (1 == fAcquireCount--) {
+            fOwner = kIllegalThreadID;
+            fSemaphore.signal();
+        }
+    }
+
+    void assertHeld() {
+        SkASSERT(fOwner == SkGetThreadID());
+    }
+
+    void assertNotHeld() {
+        SkASSERT(kIllegalThreadID == fOwner);
+    }
+
+    SkBaseSemaphore fSemaphore;
+    SkThreadID fOwner;
+    uint32_t fAcquireCount;
+};
+#endif
+
 // This needs to use subclassing instead of encapsulation to make SkAutoMutexAcquire to work.
 class SkMutex : public SkBaseMutex {
 public:
     SkMutex () {
         fSemaphore = SK_MUTEX_SEMAPHORE_INIT;
         SkDEBUGCODE(fOwner = kIllegalThreadID);
     }
     ~SkMutex () { fSemaphore.deleteSemaphore(); }
     SkMutex(const SkMutex&) = delete;
     SkMutex& operator=(const SkMutex&) = delete;
@@ skipping 49 matching lines @@
     Lock &fLock;
 };
 
 typedef SkAutoTAcquire<SkBaseMutex> SkAutoMutexAcquire;
 #define SkAutoMutexAcquire(...) SK_REQUIRE_LOCAL_VAR(SkAutoMutexAcquire)
 
 typedef SkAutoTExclusive<SkBaseMutex> SkAutoMutexExclusive;
 #define SkAutoMutexExclusive(...) SK_REQUIRE_LOCAL_VAR(SkAutoMutexExclusive)
 
 #endif//SkMutex_DEFINED