Add a very simple helper function to log slow functions.

Change-Id: I2e2e072206d02b572a330dd25857c161b5b563bf
diff --git a/libs/utils/Android.mk b/libs/utils/Android.mk
index ddfb83e..c9f8fd4 100644
--- a/libs/utils/Android.mk
+++ b/libs/utils/Android.mk
@@ -26,6 +26,7 @@
 	FileMap.cpp \
 	Flattenable.cpp \
 	LinearTransform.cpp \
+	Log.cpp \
 	PropertyMap.cpp \
 	RefBase.cpp \
 	SharedBuffer.cpp \
diff --git a/libs/utils/Log.cpp b/libs/utils/Log.cpp
new file mode 100644
index 0000000..bffb56e
--- /dev/null
+++ b/libs/utils/Log.cpp
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2012 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.
+ */
+
+#define LOG_TAG "Log"
+
+#include <utils/Log.h>
+#include <utils/Timers.h>
+
+namespace android {
+
+LogIfSlow::LogIfSlow(const char* tag, android_LogPriority priority,
+        int timeoutMillis, const char* message) :
+        mTag(tag), mPriority(priority), mTimeoutMillis(timeoutMillis), mMessage(message),
+        mStart(systemTime(SYSTEM_TIME_BOOTTIME)) {
+}
+
+LogIfSlow::~LogIfSlow() {
+    int durationMillis = nanoseconds_to_milliseconds(systemTime(SYSTEM_TIME_BOOTTIME) - mStart);
+    if (durationMillis > mTimeoutMillis) {
+        LOG_PRI(mPriority, mTag, "%s: %dms", mMessage, durationMillis);
+    }
+}
+
+} // namespace android