Revert of Use DiscardableMemoryManager on Android.

base/memory/discardable_memory_mac.cc

Index: base/memory/discardable_memory_mac.cc
diff --git a/base/memory/discardable_memory_mac.cc b/base/memory/discardable_memory_mac.cc
index 8cd5905c904deb8392f6bef67399484e0dd78e75..40a97392e955e1a740171f82ffca6f9508fa3805 100644
--- a/base/memory/discardable_memory_mac.cc
+++ b/base/memory/discardable_memory_mac.cc
@@ -115,7 +115,7 @@
     DiscardableMemoryType type, size_t size) {
   switch (type) {
     case DISCARDABLE_MEMORY_TYPE_NONE:
-    case DISCARDABLE_MEMORY_TYPE_ASHMEM:
+    case DISCARDABLE_MEMORY_TYPE_ANDROID:
       return scoped_ptr<DiscardableMemory>();
     case DISCARDABLE_MEMORY_TYPE_MAC: {
       scoped_ptr<DiscardableMemoryMac> memory(new DiscardableMemoryMac(size));
@@ -147,6 +147,11 @@
 }
 
 // static
+bool DiscardableMemory::PurgeForTestingSupported() {
+  return true;
+}
+
+// static
 void DiscardableMemory::PurgeForTesting() {
   int state = 0;
   vm_purgable_control(mach_task_self(), 0, VM_PURGABLE_PURGE_ALL, &state);