Add discardable memory emulation for non-android/mac platforms

base/base.gyp

Index: base/base.gyp
diff --git a/base/base.gyp b/base/base.gyp
index 5dfe08dd56af42a1c4b81137a078eafdcca70155..baf8cd9b4dd5be520a4aa6ccd23e83404c519b8e 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -530,6 +530,7 @@
         'md5_unittest.cc',
         'memory/aligned_memory_unittest.cc',
         'memory/discardable_memory_unittest.cc',
+        'memory/discardable_memory_provider_unittest.cc',
         'memory/linked_ptr_unittest.cc',
         'memory/ref_counted_memory_unittest.cc',
         'memory/ref_counted_unittest.cc',
@@ -830,6 +831,11 @@
             'third_party/nspr/nspr.gyp:nspr',
           ],
         }],
+        ['<(native_discardable_memory)==1', {
+          'sources!': [
+            'memory/discardable_memory_provider_unittest.cc',
+          ],
+        }],
       ],  # conditions
       'target_conditions': [
         ['OS == "ios" and _toolset != "host"', {