Move IDMap back to base/ where it is needed.

chrome/chrome.gyp

Index: chrome/chrome.gyp
diff --git a/chrome/chrome.gyp b/chrome/chrome.gyp
index 3a924ad25521fd8cdfd4f45ded2f40dadd085e1c..69684c75b30ab194ded11cdab2d18cc1a717165e 100644
--- a/chrome/chrome.gyp
+++ b/chrome/chrome.gyp
@@ -384,7 +384,6 @@
         'common/extensions/user_script.cc',
         'common/extensions/user_script.h',
         'common/gfx/utils.h',
-        'common/id_map.h',
         'common/net/cookie_monster_sqlite.cc',
         'common/net/cookie_monster_sqlite.h',
         'common/net/dns.h',
@@ -3977,7 +3976,6 @@
         'common/extensions/extension_unittest.cc',
         'common/extensions/url_pattern_unittest.cc',
         'common/extensions/user_script_unittest.cc',
-        'common/id_map_unittest.cc',
         'common/important_file_writer_unittest.cc',
         'common/json_value_serializer_unittest.cc',
         'common/mru_cache_unittest.cc',
@@ -4211,7 +4209,7 @@
       # Provides a syncapi dynamic library target from checked-in binaries,
       # or from compiling a stub implementation.
       'target_name': 'syncapi',
-      
+
       'conditions': [
         ['chrome_personalization==0', {
           # Empty target.