Upstream oodles of Chrome for Android code into Chromium.

chrome/android/java_staging/src/org/chromium/chrome/browser/util/NonThreadSafe.java

Index: chrome/android/java_staging/src/org/chromium/chrome/browser/util/NonThreadSafe.java
diff --git a/chrome/android/java_staging/src/org/chromium/chrome/browser/util/NonThreadSafe.java b/chrome/android/java_staging/src/org/chromium/chrome/browser/util/NonThreadSafe.java
new file mode 100644
index 0000000000000000000000000000000000000000..9bfc32cede62bfd107833018628a35f492ea0425
--- /dev/null
+++ b/chrome/android/java_staging/src/org/chromium/chrome/browser/util/NonThreadSafe.java
@@ -0,0 +1,45 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.util;
+
+import org.chromium.base.VisibleForTesting;
+import org.chromium.base.annotations.SuppressFBWarnings;
+
+/**
+ * NonThreadSafe is a helper class used to help verify that methods of a
+ * class are called from the same thread.
+ */
+public class NonThreadSafe {
+    private Long mThreadId = null;
+
+    public NonThreadSafe() {
+        ensureThreadIdAssigned();
+    }
+
+    /**
+     * Changes the thread that is checked for in CalledOnValidThread. This may
+     * be useful when an object may be created on one thread and then used
+     * exclusively on another thread.
+     */
+    @SuppressFBWarnings("CHROMIUM_SYNCHRONIZED_METHOD")
+    @VisibleForTesting
+    public synchronized void detachFromThread() {
+        mThreadId = null;
+    }
+
+    /**
+     * Checks if the method is called on the valid thread.
+     * Assigns the current thread if no thread was assigned.
+     */
+    @SuppressFBWarnings("CHROMIUM_SYNCHRONIZED_METHOD")
+    public synchronized boolean calledOnValidThread() {
+        ensureThreadIdAssigned();
+        return mThreadId.equals(Thread.currentThread().getId());
+    }
+
+    private void ensureThreadIdAssigned() {
+        if (mThreadId == null) mThreadId = Thread.currentThread().getId();
+    }
+}