Add discardable memory emulation for non-android/mac platforms

base/base.gypi

Index: base/base.gypi
diff --git a/base/base.gypi b/base/base.gypi
index c181554f87d2a8efdc230f98a58ab8026db7fe06..c8634fae346bd5d80e6e8132dcd38b930b6b2fa6 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -269,7 +269,10 @@
           'memory/discardable_memory.cc',
           'memory/discardable_memory.h',
           'memory/discardable_memory_android.cc',
+          'memory/discardable_memory_emulated.cc',
           'memory/discardable_memory_mac.cc',
+          'memory/discardable_memory_provider.cc',
+          'memory/discardable_memory_provider.h',
           'memory/linked_ptr.h',
           'memory/manual_constructor.h',
           'memory/memory_pressure_listener.cc',
@@ -777,6 +780,14 @@
               'sources/': [ ['exclude', '^win/'] ],
             },
           ],
+          ['OS == "android" or OS == "mac"', {
+              'sources!': [
+                'memory/discardable_memory_emulated.cc',
+                'memory/discardable_memory_provider.cc',
+                'memory/discardable_memory_provider.h',
+              ],
+            },
+          ],
           ['OS != "android" or >(nacl_untrusted_build)==1', {
               'sources/': [ ['exclude', '^android/'] ],
             },