Update from https://crrev.com/316786

base/memory/discardable_memory_manager.cc

Index: base/memory/discardable_memory_manager.cc
diff --git a/base/memory/discardable_memory_manager.cc b/base/memory/discardable_memory_manager.cc
index 09e63e35f62ef852b04997cd15fde67f433fc6d0..cbbdb4770af04494f48290fb7bfae500e5496b47 100644
--- a/base/memory/discardable_memory_manager.cc
+++ b/base/memory/discardable_memory_manager.cc
@@ -51,34 +51,6 @@ void DiscardableMemoryManager::SetHardMemoryLimitExpirationTime(
   hard_memory_limit_expiration_time_ = hard_memory_limit_expiration_time;
 }
 
-void DiscardableMemoryManager::ReleaseFreeMemory() {
-  TRACE_EVENT0("base", "DiscardableMemoryManager::ReleaseFreeMemory");
-
-  AutoLock lock(lock_);
-  size_t bytes_allocated_before_releasing_memory = bytes_allocated_;
-  for (auto& entry : allocations_) {
-    Allocation* allocation = entry.first;
-    AllocationInfo* info = &entry.second;
-
-    if (!info->purgable)
-      continue;
-
-    // Skip if memory is still resident, otherwise purge and adjust
-    // |bytes_allocated_|.
-    if (allocation->IsMemoryResident())
-      continue;
-
-    size_t bytes_purgable = info->bytes;
-    DCHECK_LE(bytes_purgable, bytes_allocated_);
-    bytes_allocated_ -= bytes_purgable;
-    info->purgable = false;
-    allocation->Purge();
-  }
-
-  if (bytes_allocated_ != bytes_allocated_before_releasing_memory)
-    BytesAllocatedChanged(bytes_allocated_);
-}
-
 bool DiscardableMemoryManager::ReduceMemoryUsage() {
   return PurgeIfNotUsedSinceHardLimitCutoffUntilWithinSoftMemoryLimit();
 }