base: Add soft memory limit to DiscardableMemoryManager.

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 3215969fef5d1ab3764625244fd3eec007092615..8988c2b8d2bd46d759ec2f9c42243b6274d114be 100644
--- a/base/memory/discardable_memory_android.cc
+++ b/base/memory/discardable_memory_android.cc
@@ -32,7 +32,10 @@ size_t GetOptimalAshmemRegionSizeForAllocator() {
 // Holds the shared state used for allocations.
 struct SharedState {
   SharedState()
-      : manager(kAshmemMemoryLimit, kAshmemMemoryLimit),
+      : manager(kAshmemMemoryLimit,
+                kAshmemMemoryLimit,
+                kAshmemMemoryLimit,
+                TimeDelta::Max()),
         allocator(kAshmemAllocatorName,
                   GetOptimalAshmemRegionSizeForAllocator()) {}
 
@@ -54,6 +57,11 @@ void DiscardableMemory::UnregisterMemoryPressureListeners() {
 }
 
 // static
+bool DiscardableMemory::ReduceMemoryUsage() {
+  return internal::DiscardableMemoryEmulated::ReduceMemoryUsage();
+}
+
+// static
 void DiscardableMemory::GetSupportedTypes(
     std::vector<DiscardableMemoryType>* types) {
   const DiscardableMemoryType supported_types[] = {