Bug 1523949 - part 2 - switch BlockingResourceBase to MOZ_THREAD_LOCAL; r=erahm,emilio

This change results in somewhat nicer code and should be slightly more
performant.

Author: froydnj

layout/style/ServoBindings.toml

@@ -380,6 +380,7 @@ opaque-types = [
                                 # don't align properly on Linux 32-bit
     "mozilla::SchedulerGroup", # Non-standard-layout packing of field into superclass
     "mozilla::detail::GkAtoms", # https://bugzilla.mozilla.org/show_bug.cgi?id=1517685
+    "mozilla::detail::ThreadLocal.*",
 ]
 
 # All cbindgen-types are in mod "structs::root::mozilla".

xpcom/threads/BlockingResourceBase.cpp

@@ -44,7 +44,7 @@ const char* const BlockingResourceBase::kResourceTypeName[] = {
 #ifdef DEBUG
 
 PRCallOnceType BlockingResourceBase::sCallOnce;
-unsigned BlockingResourceBase::sResourceAcqnChainFrontTPI = (unsigned)-1;
+MOZ_THREAD_LOCAL(BlockingResourceBase*) BlockingResourceBase::sResourceAcqnChainFront;
 BlockingResourceBase::DDT* BlockingResourceBase::sDeadlockDetector;
 
 void BlockingResourceBase::StackWalkCallback(uint32_t aFrameNumber, void* aPc,
@@ -230,7 +230,7 @@ size_t BlockingResourceBase::SizeOfDeadlockDetector(
 }
 
 PRStatus BlockingResourceBase::InitStatics() {
-  PR_NewThreadPrivateIndex(&sResourceAcqnChainFrontTPI, 0);
+  MOZ_ASSERT(sResourceAcqnChainFront.init());
   sDeadlockDetector = new DDT();
   if (!sDeadlockDetector) {
     MOZ_CRASH("can't allocate deadlock detector");

xpcom/threads/BlockingResourceBase.h

@@ -8,6 +8,7 @@
 #define mozilla_BlockingResourceBase_h
 
 #include "mozilla/Logging.h"
+#include "mozilla/ThreadLocal.h"
 
 #include "nscore.h"
 #include "nsDebug.h"
@@ -152,8 +153,7 @@ class BlockingResourceBase {
    *         resource acquired.
    */
   static BlockingResourceBase* ResourceChainFront() {
-    return (BlockingResourceBase*)PR_GetThreadPrivate(
-        sResourceAcqnChainFrontTPI);
+    return sResourceAcqnChainFront.get();
   }
 
   /**
@@ -175,7 +175,7 @@ class BlockingResourceBase {
    */
   void ResourceChainAppend(BlockingResourceBase* aPrev) {
     mChainPrev = aPrev;
-    PR_SetThreadPrivate(sResourceAcqnChainFrontTPI, this);
+    sResourceAcqnChainFront.set(this);
   }  // NS_NEEDS_RESOURCE(this)
 
   /**
@@ -186,7 +186,7 @@ class BlockingResourceBase {
    */
   void ResourceChainRemove() {
     NS_ASSERTION(this == ResourceChainFront(), "not at chain front");
-    PR_SetThreadPrivate(sResourceAcqnChainFrontTPI, mChainPrev);
+    sResourceAcqnChainFront.set(mChainPrev);
   }  // NS_NEEDS_RESOURCE(this)
 
   /**
@@ -280,11 +280,10 @@ class BlockingResourceBase {
   static PRCallOnceType sCallOnce;
 
   /**
-   * sResourceAcqnChainFrontTPI
-   * Thread-private index to the front of each thread's resource
+   * Thread-private pointer to the front of each thread's resource
    * acquisition chain.
    */
-  static unsigned sResourceAcqnChainFrontTPI;
+  static MOZ_THREAD_LOCAL(BlockingResourceBase*) sResourceAcqnChainFront;
 
   /**
    * sDeadlockDetector