[Sync] Add sync_export.h (Step 1 for componentizing sync)

sync/sync.gyp

Index: sync/sync.gyp
diff --git a/sync/sync.gyp b/sync/sync.gyp
index 507f73c0a62e86518c610e97d077227824f994e0..484f6ec996e0d5d6810c7bc358e490d6b43e50ef 100644
--- a/sync/sync.gyp
+++ b/sync/sync.gyp
@@ -14,11 +14,17 @@
     # should depend on.
     {
       'target_name': 'sync',
+      # TODO(akalin): Change this to '<(component)'.  When we rename
+      # this to 'sync_core' and make the overarching 'sync' library,
+      # make that one '<(component)'.
       'type': 'static_library',

[Ryan Sleevi, 2012/07/12 18:22:13]

I don't think this CL will/should work unless/until you do change this to
<(component)

When building as a shared library, COMPONENT_BUILD will be set by
build/common.gypi. As a result, all of the symbols marked SYNC_EXPORT will be
marked declexport (when building this static lib), but marked declimport by all
dependents. As such, there will be confusion between whether or not the symbol
is really within the module, and multiple (dependent) modules may end up
inadvertantly exporting the same symbols.

[akalin, 2012/07/13 00:51:43]

I added '0 &&' to sync_export.h, so it should be a no-op for now.

       'variables': { 'enable_wexit_time_destructors': 1, },
       'include_dirs': [
         '..',
       ],
+      'defines': [
+        'SYNC_IMPLEMENTATION',
+      ],
       'dependencies': [
         '../base/base.gyp:base',
         '../build/temp_gyp/googleurl.gyp:googleurl',
@@ -33,6 +39,7 @@
         'protocol/sync_proto.gyp:sync_proto',
       ],
       'sources': [
+        'base/sync_export.h',
         'internal_api/public/base/enum_set.h',
         'internal_api/public/base/model_type.h',
         'internal_api/public/base/model_type_payload_map.cc',
@@ -776,6 +783,9 @@
     {
       'target_name': 'sync_client',
       'type': 'executable',
+      'defines': [
+        'SYNC_TEST',
+      ],
       'dependencies': [
         '../base/base.gyp:base',
         '../jingle/jingle.gyp:notifier',