Allocate memory in smaller chunks for chrome://memory-exhaust/

The memory-exhaustion loop could cause DbgHelp's SymFromAddr() to hang
in certain build configs (32-bit Windows Clang debug builds), causing
MetricsServiceBrowserTest.OOMRenderers to hang while generating the
backtrace after the OOM exception. Reducing the allocation size seems to
help.

BUG=692564
TBR=jochen

Review-Url: https://codereview.chromium.org/2882513003
Cr-Commit-Position: refs/heads/master@{#471138}

content/renderer/render_frame_impl.cc

@@ -775,7 +775,7 @@ double ConvertToBlinkTime(const base::TimeTicks& time_ticks) {
 NOINLINE void ExhaustMemory() {
   volatile void* ptr = nullptr;
   do {
-    ptr = malloc(0x10000000);
+    ptr = malloc(0x1000000);
     base::debug::Alias(&ptr);
   } while (ptr);
 }