Update from chromium https://crrev.com/301315

base/memory/discardable_memory_linux.cc

Index: base/memory/discardable_memory_linux.cc
diff --git a/base/memory/discardable_memory_linux.cc b/base/memory/discardable_memory_linux.cc
index 6a9a28df2dc6fb9bdb10c5065e444b047e00aad9..9b4e9401ce4ff7c006756a9a5ed6a245431662c9 100644
--- a/base/memory/discardable_memory_linux.cc
+++ b/base/memory/discardable_memory_linux.cc
@@ -6,10 +6,16 @@
 
 #include "base/logging.h"
 #include "base/memory/discardable_memory_emulated.h"
+#include "base/memory/discardable_memory_shmem.h"
 
 namespace base {
 
 // static
+void DiscardableMemory::ReleaseFreeMemory() {
+  internal::DiscardableMemoryShmem::ReleaseFreeMemory();
+}
+
+// static
 bool DiscardableMemory::ReduceMemoryUsage() {
   return internal::DiscardableMemoryEmulated::ReduceMemoryUsage();
 }
@@ -18,7 +24,8 @@ bool DiscardableMemory::ReduceMemoryUsage() {
 void DiscardableMemory::GetSupportedTypes(
     std::vector<DiscardableMemoryType>* types) {
   const DiscardableMemoryType supported_types[] = {
-    DISCARDABLE_MEMORY_TYPE_EMULATED
+    DISCARDABLE_MEMORY_TYPE_EMULATED,
+    DISCARDABLE_MEMORY_TYPE_SHMEM
   };
   types->assign(supported_types, supported_types + arraysize(supported_types));
 }
@@ -35,6 +42,14 @@ scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemoryWithType(
 
       return memory.Pass();
     }
+    case DISCARDABLE_MEMORY_TYPE_SHMEM: {
+      scoped_ptr<internal::DiscardableMemoryShmem> memory(
+          new internal::DiscardableMemoryShmem(size));
+      if (!memory->Initialize())
+        return nullptr;
+
+      return memory.Pass();
+    }
     case DISCARDABLE_MEMORY_TYPE_NONE:
     case DISCARDABLE_MEMORY_TYPE_ASHMEM:
     case DISCARDABLE_MEMORY_TYPE_MACH:
@@ -49,6 +64,7 @@ scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemoryWithType(
 // static
 void DiscardableMemory::PurgeForTesting() {
   internal::DiscardableMemoryEmulated::PurgeForTesting();
+  internal::DiscardableMemoryShmem::PurgeForTesting();
 }
 
 }  // namespace base