Initialize stack dumping in OOP memlog.

Failing to explicitly initialize stack dumping before adding a malloc hook that
uses it can cause problems. In particular, on Linux calling backtrace() can
load a library which calls malloc, meaning the hook will be recursive.

Bug: 764522
Change-Id: If602902aa4238903541ca52f765927369dbf6e71
Reviewed-on: https://chromium-review.googlesource.com/664301Reviewed-by: Erik Chen <erikchen@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501644}

chrome/common/profiling/memlog_allocator_shim.cc

@@ -185,8 +185,10 @@ void HookPartitionFree(void* address) {
 }  // namespace
 
 void InitAllocatorShim(MemlogSenderPipe* sender_pipe) {
-  g_send_buffers = new SendBuffer[kNumSendBuffers];
+  // Must be done before hooking any functions that make stack traces.
+  base::debug::EnableInProcessStackDumping();
 
+  g_send_buffers = new SendBuffer[kNumSendBuffers];
   g_sender_pipe = sender_pipe;
 
 #if BUILDFLAG(USE_ALLOCATOR_SHIM)