Split TLS implementation into its own translation unit.

src/ports/SkTLS_win.cpp

Index: src/ports/SkTLS_win.cpp
===================================================================
--- src/ports/SkTLS_win.cpp	(revision 0)
+++ src/ports/SkTLS_win.cpp	(working copy)
@@ -0,0 +1,75 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkTLS.h"
+#include "SkThread.h"
+
+static bool gOnce = false;
+static DWORD gTlsIndex;
+SK_DECLARE_STATIC_MUTEX(gMutex);
+
+void* SkTLS::PlatformGetSpecific(bool forceCreateTheSlot) {
+    if (!forceCreateTheSlot && !gOnce) {
+        return NULL;
+    }
+
+    if (!gOnce) {
+        SkAutoMutexAcquire tmp(gMutex);
+        if (!gOnce) {
+            gTlsIndex = TlsAlloc();
+            gOnce = true;
+        }
+    }
+    return TlsGetValue(gTlsIndex);
+}
+
+void SkTLS::PlatformSetSpecific(void* ptr) {
+    SkASSERT(gOnce);
+    (void)TlsSetValue(gTlsIndex, ptr);
+}
+
+// Call TLS destructors on thread exit. Code based on Chromium's
+// base/threading/thread_local_storage_win.cc
+#ifdef _WIN64
+
+#pragma comment(linker, "/INCLUDE:_tls_used")
+#pragma comment(linker, "/INCLUDE:skia_tls_callback")
+
+#else
+
+#pragma comment(linker, "/INCLUDE:__tls_used")
+#pragma comment(linker, "/INCLUDE:_skia_tls_callback")
+
+#endif
+
+void NTAPI onTLSCallback(PVOID unused, DWORD reason, PVOID unused2) {
+    if ((DLL_THREAD_DETACH == reason || DLL_PROCESS_DETACH == reason) && gOnce) {
+        void* ptr = TlsGetValue(gTlsIndex);
+        if (ptr != NULL) {
+            SkTLS::Destructor(ptr);
+            TlsSetValue(gTlsIndex, NULL);
+        }
+    }
+}
+
+extern "C" {
+
+#ifdef _WIN64
+
+#pragma const_seg(".CRT$XLB")
+extern const PIMAGE_TLS_CALLBACK skia_tls_callback;
+const PIMAGE_TLS_CALLBACK skia_tls_callback = onTLSCallback;
+#pragma const_seg()
+
+#else
+
+#pragma data_seg(".CRT$XLB")
+PIMAGE_TLS_CALLBACK skia_tls_callback = onTLSCallback;
+#pragma data_seg()
+
+#endif
+}