Update to Chromium //base at Chromium commit 3e81715e6d3a4324362635aea46ce1f1a163cca1.

test/test_discardable_memory_allocator.cc

Index: test/test_discardable_memory_allocator.cc
diff --git a/test/test_discardable_memory_allocator.cc b/test/test_discardable_memory_allocator.cc
index 23d529c324d74677ca0bba6ed37d94b606ea3aff..eef1c982446633c79cdf94bee44ad578c55aed86 100644
--- a/test/test_discardable_memory_allocator.cc
+++ b/test/test_discardable_memory_allocator.cc
@@ -20,6 +20,12 @@ class DiscardableMemoryImpl : public DiscardableMemory {
   void Unlock() override {}
   void* data() const override { return data_.get(); }
 
+  trace_event::MemoryAllocatorDump* CreateMemoryAllocatorDump(
+      const char* name,
+      trace_event::ProcessMemoryDump* pmd) const override {
+    return nullptr;
+  }
+
  private:
   scoped_ptr<uint8_t[]> data_;
 };