ifdef-out ConfigurePartitionAlloc in non PA-E builds

The impl of ConfigurePartitionAlloc is already behind a
allocator_shim_default_dispatch_to_partition_alloc.cc but its
declaration isn't, this cause some linker issues when doing some
non-PAE builds:
lld-link: error: undefined symbol: void __cdecl base::allocator::ConfigurePartitionAlloc(void)
>>> referenced by .\..\..\chrome\app\chrome_main.cc:74
>>>               obj/chrome/chrome_dll/chrome_main.obj:(ChromeMain)

Bug: 1121427
Change-Id: Ie589f1b3ac57d6a13be361e9669c2fc6855e8115
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2616460Reviewed-by: Ken Rockot <rockot@google.com>
Reviewed-by: Will Harris <wfh@chromium.org>
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841332}

base/allocator/allocator_shim.h

@@ -146,7 +146,7 @@ BASE_EXPORT void InsertAllocatorDispatch(AllocatorDispatch* dispatch);
 // in malloc(), which we really don't want.
 BASE_EXPORT void RemoveAllocatorDispatchForTesting(AllocatorDispatch* dispatch);
 
-#if defined(OS_WIN)
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && defined(OS_WIN)
 // Configures the allocator for the caller's allocation domain. Allocations that
 // take place prior to this configuration step will succeed, but will not
 // benefit from its one-time mitigations. As such, this function must be called

chrome/app/chrome_main.cc

@@ -68,7 +68,7 @@ int ChromeMain(int argc, const char** argv) {
 #endif
 
 #if defined(OS_WIN)
-#if BUILDFLAG(USE_ALLOCATOR_SHIM)
+#if BUILDFLAG(USE_ALLOCATOR_SHIM) && BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
   // Call this early on in order to configure heap workarounds. This must be
   // called from chrome.dll. This may be a NOP on some platforms.
   base::allocator::ConfigurePartitionAlloc();