[Sync] Creating sync_sessions component, moving revisit logic.

components/sync_sessions.gypi

+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'targets': [
+    {
+      # GN version: //components/sync_sessions
+      'target_name': 'sync_sessions',
+      'type': 'static_library',
+      'include_dirs': [
+        '..',
+      ],
+      'dependencies': [
+        '../base/base.gyp:base',
+        '../sync/sync.gyp:sync',
+        'sync_driver',
+      ],
+      'sources': [
+        # Note: sources list duplicated in GN build.
+        'sync_sessions/revisit/current_tab_matcher.cc',
+        'sync_sessions/revisit/current_tab_matcher.h',
+        'sync_sessions/revisit/offset_tab_matcher.cc',
+        'sync_sessions/revisit/offset_tab_matcher.h',
+        'sync_sessions/revisit/page_equality.h',
+        'sync_sessions/revisit/page_visit_observer.h',
+        'sync_sessions/revisit/sessions_page_revisit_observer.cc',
+        'sync_sessions/revisit/sessions_page_revisit_observer.h',
+      ],
+      'conditions': [
+        ['OS!="ios"', {
+          'dependencies': [
+            'sessions_content',
+          ],
+        }, {  # OS==ios
+          'dependencies': [
+            'sessions_ios',
+          ],
+        }],
+      ],
+    },
+    {
+      # GN version: //components/sync_sessions:test_support
+      'target_name': 'sync_sessions_test_support',

[blundell, 2015/10/09 08:55:06]

?

[skym, 2015/10/09 15:16:35]

I figured it would be easier to add the test support target now than later when
we actually needed it, even though we currently don't have any test support
files.

[skym, 2015/10/09 17:11:11]

It seems the win8_chromium_ng build is failing from something related to this
test_support target... And seemingly only win8.

FAILED: E:/b/depot_tools/python276_bin/python.exe gyp-win-tool link-wrapper
environment.x86 False link.exe /nologo /OUT:components_unittests.exe
/PDB:components_unittests.exe.pdb @components_unittests.exe.rsp
LINK : fatal error LNK1181: cannot open input file
'obj/components/sync_sessions/test_support.lib'

I suppose I could remove the test_support if it's going to be a hassle to get to
build right now. My current assumption is that win8 skips making the .lib file
since there are no sources, and then the linking cannot find the file since it
doesn't exist.

Removing it all now.

[skym, 2015/10/09 17:37:53]

Err, bizarre, changing static_library to source_set for the GN build target of
test_support seemed to fix the win8 build.
http://build.chromium.org/p/tryserver.chromium.win/builders/win8_chromium_ng/...
. I guess win8_chromium_ng is actually a GN build, my earlier understanding was
mistaken. Re-running default set of try bots now.

+      'type': 'static_library',
+      'include_dirs': [
+        '..',
+      ],
+      'dependencies': [
+        'sync_sessions',
+      ],
+      'sources': [
+      ],
+    },
+  ],
+}