base: Add uncached malloc based discardable memory type.

base/memory/discardable_memory_android.cc

Index: base/memory/discardable_memory_android.cc
diff --git a/base/memory/discardable_memory_android.cc b/base/memory/discardable_memory_android.cc
index 2004a360b0c980be7068012500b53ee98ec137a6..7b1731a0f63c21df0bd4ec6580c714fb9053e332 100644
--- a/base/memory/discardable_memory_android.cc
+++ b/base/memory/discardable_memory_android.cc
@@ -17,6 +17,7 @@
 #include "base/logging.h"
 #include "base/memory/discardable_memory_allocator_android.h"
 #include "base/memory/discardable_memory_emulated.h"
+#include "base/memory/discardable_memory_malloc.h"
 #include "third_party/ashmem/ashmem.h"
 
 namespace base {
@@ -126,7 +127,8 @@ void DiscardableMemory::GetSupportedTypes(
     std::vector<DiscardableMemoryType>* types) {
   const DiscardableMemoryType supported_types[] = {
     DISCARDABLE_MEMORY_TYPE_ANDROID,
-    DISCARDABLE_MEMORY_TYPE_EMULATED
+    DISCARDABLE_MEMORY_TYPE_EMULATED,
+    DISCARDABLE_MEMORY_TYPE_MALLOC
   };
   types->assign(supported_types, supported_types + arraysize(supported_types));
 }
@@ -149,6 +151,14 @@ scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemoryWithType(
 
       return memory.PassAs<DiscardableMemory>();
     }
+    case DISCARDABLE_MEMORY_TYPE_MALLOC: {
+      scoped_ptr<internal::DiscardableMemoryMalloc> memory(
+          new internal::DiscardableMemoryMalloc(size));
+      if (!memory->Initialize())
+        return scoped_ptr<DiscardableMemory>();
+
+      return memory.PassAs<DiscardableMemory>();
+    }
   }
 
   NOTREACHED();