Mark FatalProcessOutOfMemory as noreturn

This method always calls the FATAL macro, which is also marked
[[noreturn]]. The documentation already mentioned this, but now it's
actually enforced by the compiler.

R=adamk@chromium.org

Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I2e331c9826fad6aad9c22929a0d5f890a508d0d9
Reviewed-on: https://chromium-review.googlesource.com/966561Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52115}

src/allocation.h

@@ -20,7 +20,8 @@ namespace internal {
 
 // Called when allocation routines fail to allocate, even with a possible retry.
 // This function should not return, but should terminate the current processing.
-V8_EXPORT_PRIVATE void FatalProcessOutOfMemory(const char* message);
+[[noreturn]] V8_EXPORT_PRIVATE void FatalProcessOutOfMemory(
+    const char* message);
 
 // Superclass for classes managed with new & delete.
 class V8_EXPORT_PRIVATE Malloced {

src/api.cc

@@ -330,7 +330,7 @@ void i::V8::FatalProcessOutOfMemory(const char* location, bool is_heap_oom) {
     // Note that the embedder's oom handler won't be called in this case. We
     // just crash.
     FATAL("API fatal error handler returned after process out of memory");
-    return;
+    UNREACHABLE();
   }
 
   memset(last_few_messages, 0, Heap::kTraceRingBufferSize + 1);

src/v8.h

@@ -23,8 +23,8 @@ class V8 : public AllStatic {
 
   // Report process out of memory. Implementation found in api.cc.
   // This function will not return, but will terminate the execution.
-  static void FatalProcessOutOfMemory(const char* location,
-                                      bool is_heap_oom = false);
+  [[noreturn]] static void FatalProcessOutOfMemory(const char* location,
+                                                   bool is_heap_oom = false);
 
   static void InitializePlatform(v8::Platform* platform);
   static void ShutdownPlatform();