Bug 1211939 - Don't call JSRuntime::onOutOfMemory from helper threads. r=jonco

js/src/gc/Zone.h

@@ -142,6 +142,8 @@ struct Zone : public JS::shadow::Zone,
     void onTooMuchMalloc();
 
     void* onOutOfMemory(js::AllocFunction allocFunc, size_t nbytes, void* reallocPtr = nullptr) {
+        if (!CurrentThreadCanAccessRuntime(runtime_))
+            return nullptr;
         return runtimeFromMainThread()->onOutOfMemory(allocFunc, nbytes, reallocPtr);
     }
     void reportAllocationOverflow() { js::ReportAllocationOverflow(nullptr); }

js/src/jscntxt.h

@@ -163,7 +163,9 @@ class ExclusiveContext : public ContextFriendFields,
     }
 
     void* onOutOfMemory(js::AllocFunction allocFunc, size_t nbytes, void* reallocPtr = nullptr) {
-        return runtime_->onOutOfMemory(allocFunc, nbytes, reallocPtr, maybeJSContext());
+        if (!isJSContext())
+            return nullptr;
+        return runtime_->onOutOfMemory(allocFunc, nbytes, reallocPtr, asJSContext());
     }
 
     /* Clear the pending exception (if any) due to OOM. */

js/src/vm/Runtime.cpp

@@ -760,6 +760,7 @@ JSRuntime::onOutOfMemory(AllocFunction allocFunc, size_t nbytes, void* reallocPt
                          JSContext* maybecx)
 {
     MOZ_ASSERT_IF(allocFunc != AllocFunction::Realloc, !reallocPtr);
+    MOZ_ASSERT(CurrentThreadCanAccessRuntime(this));
 
     if (isHeapBusy())
         return nullptr;