base: Refactor DiscardableMemoryProvider to build and be tested on all platforms.

base/base.gypi

Index: base/base.gypi
diff --git a/base/base.gypi b/base/base.gypi
index eb580525e268397ffa5492a3b0cc2686c68c0081..11edab009685fe11c2bbb4d5437390be16328475 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -292,13 +292,17 @@
           'memory/aligned_memory.cc',
           'memory/aligned_memory.h',
           'memory/discardable_memory.h',
-          'memory/discardable_memory_allocator_android.h',
           'memory/discardable_memory_allocator_android.cc',
+          'memory/discardable_memory_allocator_android.h',
           'memory/discardable_memory_android.cc',
+          'memory/discardable_memory_android.h',
           'memory/discardable_memory_emulated.cc',
+          'memory/discardable_memory_emulated.h',
+          'memory/discardable_memory_linux.cc',
           'memory/discardable_memory_mac.cc',
           'memory/discardable_memory_provider.cc',
           'memory/discardable_memory_provider.h',
+          'memory/discardable_memory_win.cc',
           'memory/linked_ptr.h',
           'memory/manual_constructor.h',
           'memory/memory_pressure_listener.cc',
@@ -868,14 +872,6 @@
               'sources/': [ ['exclude', '^win/'] ],
             },
           ],
-          ['<(native_discardable_memory)==1', {
-              '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/'] ],
             },