Revert of base: Introduce an explicit call for reducing emulated discardable memory usage.

base/memory/discardable_memory_unittest.cc

Index: base/memory/discardable_memory_unittest.cc
diff --git a/base/memory/discardable_memory_unittest.cc b/base/memory/discardable_memory_unittest.cc
index 516a96b5a4fa2576a6cb031877ddf7d7bff0cfac..dc0e2cd21262b4d7da8dd3edb891b91bb8f2d5b7 100644
--- a/base/memory/discardable_memory_unittest.cc
+++ b/base/memory/discardable_memory_unittest.cc
@@ -6,6 +6,7 @@
 
 #include <algorithm>
 
+#include "base/run_loop.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #if defined(OS_ANDROID)
@@ -18,8 +19,12 @@
 class DiscardableMemoryTest
     : public testing::TestWithParam<DiscardableMemoryType> {
  public:
-  DiscardableMemoryTest() {}
+  DiscardableMemoryTest() : message_loop_(MessageLoop::TYPE_IO) {
+    // Register memory pressure listeners now that we have a message loop.
+    DiscardableMemory::RegisterMemoryPressureListeners();
+  }
   virtual ~DiscardableMemoryTest() {
+    DiscardableMemory::UnregisterMemoryPressureListeners();
   }
 
  protected:
@@ -27,6 +32,9 @@
     return DiscardableMemory::CreateLockedMemoryWithType(
         GetParam(), size).Pass();
   }
+
+ private:
+  MessageLoop message_loop_;
 };
 
 const size_t kSize = 1024;