Precache paths from a worker thread

Change-Id: I3e7b53d67e0e03e403beaf55c39350ead7f1e309
diff --git a/libs/hwui/thread/Signal.h b/libs/hwui/thread/Signal.h
new file mode 100644
index 0000000..dcf5449
--- /dev/null
+++ b/libs/hwui/thread/Signal.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_HWUI_SIGNAL_H
+#define ANDROID_HWUI_SIGNAL_H
+
+#include <stdint.h>
+#include <sys/types.h>
+#include <utils/threads.h>
+
+namespace android {
+namespace uirenderer {
+
+class Signal {
+public:
+    Signal(Condition::WakeUpType type = Condition::WAKE_UP_ALL) : mType(type), mSignaled(false) { }
+    ~Signal() { }
+
+    void signal() {
+        Mutex::Autolock l(mLock);
+        mSignaled = true;
+        mCondition.signal(mType);
+    }
+
+    void wait() {
+        Mutex::Autolock l(mLock);
+        while (!mSignaled) {
+            mCondition.wait(mLock);
+        }
+        mSignaled = false;
+    }
+
+private:
+    Condition::WakeUpType mType;
+    volatile bool mSignaled;
+    mutable Mutex mLock;
+    mutable Condition mCondition;
+};
+
+}; // namespace uirenderer
+}; // namespace android
+
+#endif // ANDROID_HWUI_SIGNAL_H