Blink: Make ThreadCondition only work with Mutex.

The interaction between ThreadCondition (condition variables) and
recursive (a.k.a. re-entrant) mutexes is difficult to reason about.
Details in the "Why can the holder of a Lock not reacquire it?" section
of https://www.chromium.org/developers/lock-and-condition-variable

Bug: 805814
Change-Id: Ie0b5e026a43768108011ca8f2f6fd3fe0e1f4b03
Reviewed-on: https://chromium-review.googlesource.com/885862
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531846}

third_party/WebKit/Source/platform/wtf/ThreadingPrimitives.h

@@ -130,12 +130,12 @@ class WTF_EXPORT ThreadCondition final {
   ThreadCondition();
   ~ThreadCondition();
 
-  void Wait(MutexBase&);
+  void Wait(Mutex&);
   // Returns true if the condition was signaled before absoluteTime, false if
   // the absoluteTime was reached or is in the past.
   // The absoluteTime is in seconds, starting on January 1, 1970. The time is
   // assumed to use the same time zone as WTF::currentTime().
-  bool TimedWait(MutexBase&, double absolute_time);
+  bool TimedWait(Mutex&, double absolute_time);
   void Signal();
   void Broadcast();
 

third_party/WebKit/Source/platform/wtf/ThreadingPthreads.cpp

@@ -204,7 +204,7 @@ ThreadCondition::~ThreadCondition() {
   pthread_cond_destroy(&condition_);
 }
 
-void ThreadCondition::Wait(MutexBase& mutex) {
+void ThreadCondition::Wait(Mutex& mutex) {
   PlatformMutex& platform_mutex = mutex.Impl();
   int result = pthread_cond_wait(&condition_, &platform_mutex.internal_mutex_);
   DCHECK_EQ(result, 0);
@@ -213,7 +213,7 @@ void ThreadCondition::Wait(MutexBase& mutex) {
 #endif
 }
 
-bool ThreadCondition::TimedWait(MutexBase& mutex, double absolute_time) {
+bool ThreadCondition::TimedWait(Mutex& mutex, double absolute_time) {
   if (absolute_time < CurrentTime())
     return false;
 

third_party/WebKit/Source/platform/wtf/ThreadingWin.cpp

@@ -242,7 +242,7 @@ ThreadCondition::ThreadCondition() {
 
 ThreadCondition::~ThreadCondition() {}
 
-void ThreadCondition::Wait(MutexBase& mutex) {
+void ThreadCondition::Wait(Mutex& mutex) {
   PlatformMutex& platform_mutex = mutex.Impl();
   BOOL result = SleepConditionVariableCS(
       &condition_, &platform_mutex.internal_mutex_, INFINITE);
@@ -250,7 +250,7 @@ void ThreadCondition::Wait(MutexBase& mutex) {
   ++platform_mutex.recursion_count_;
 }
 
-bool ThreadCondition::TimedWait(MutexBase& mutex, double absolute_time) {
+bool ThreadCondition::TimedWait(Mutex& mutex, double absolute_time) {
   DWORD interval = AbsoluteTimeToWaitTimeoutInterval(absolute_time);
 
   if (!interval) {