tcmalloc: adjust default memory release parameters

Makes the default and max release delays equal to the older values
used in Chromium, to reduce memory use.

BUG=724399,b:118386135

Change-Id: I651d5542c541b7e0e3a44b16b6c5800a4f7f9e1e
Reviewed-on: https://chromium-review.googlesource.com/c/1298339Reviewed-by: Will Harris <wfh@chromium.org>
Commit-Queue: Gabriel Marin <gmx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603145}

third_party/tcmalloc/chromium/src/page_heap.h

@@ -235,11 +235,13 @@ class PERFTOOLS_DLL_DECL PageHeap {
   // Never delay scavenging for more than the following number of
   // deallocated pages.  With 4K pages, this comes to 4GB of
   // deallocation.
-  static const int kMaxReleaseDelay = 1 << 20;
+  // Chrome:  Changed to 64MB
+  static const int kMaxReleaseDelay = 1 << 14;
 
   // If there is nothing to release, wait for so many pages before
   // scavenging again.  With 4K pages, this comes to 1GB of memory.
-  static const int kDefaultReleaseDelay = 1 << 18;
+  // Chrome:  Changed to 16MB
+  static const int kDefaultReleaseDelay = 1 << 12;
 
   // Pick the appropriate map and cache types based on pointer size
   typedef MapSelector<kAddressBits>::Type PageMap;