Fix race condition in parallel font initialization.

src/ports/SkFontConfigInterface_direct.cpp

Index: src/ports/SkFontConfigInterface_direct.cpp
diff --git a/src/ports/SkFontConfigInterface_direct.cpp b/src/ports/SkFontConfigInterface_direct.cpp
index dc9afbae1f47b642704ca02df68923145f38898f..25c965daddacc4b56a89d4d995c3469c7479fd9a 100644
--- a/src/ports/SkFontConfigInterface_direct.cpp
+++ b/src/ports/SkFontConfigInterface_direct.cpp
@@ -124,7 +124,8 @@ private:
     SkMutex mutex_;
 };
 
-SkFontConfigInterface* SkFontConfigInterface::GetSingletonDirectInterface() {
+SkFontConfigInterface* SkFontConfigInterface::GetSingletonDirectInterface(SkBaseMutex& mutex) {
+    SkAutoMutexAcquire ac(mutex);
     SK_DECLARE_STATIC_LAZY_PTR(SkFontConfigInterfaceDirect, direct);

[mtklein, 2014/06/26 18:59:07]

Given the mutex lock, this can become simply

static SkFontConfigInterfaceDirect* singleton = NULL;
if (singleton == NULL) {
  singleton = SkNEW(SkFontConfigInterfaceDirect);
}
return singleton;

That is, if we're under a mutex, SkLazyPtr isn't needed.

The slightly more performant alternative is to do this:

static bool initialized = false;
static SkFontConfigInteface* singleton = NULL;
SkOnce(&initialized, &mutex, CreateDirect, &singleton);
return singleton;

where CreateDirect is something like

/*static*/
void SkFontConfigInterface::CreateDirect(SkFontConfigInterface** ptr) {
  *ptr = SkNEW(SkFontConfigInterfaceDirect);
}

[tomhudson, 2014/06/26 21:01:52]

SK_DECLARE_STATIC_LAZY_PTR does nicely describe what we're doing.
I didn't want to introduce the extra CreateDirect() function, so implemented
your slightly-less-performant version.

Done

     return direct.get();
 }