Introduces an additional extension loader that load extra extensions based on per-extension json fi…

chrome/common/chrome_paths.cc

Index: chrome/common/chrome_paths.cc
===================================================================
--- chrome/common/chrome_paths.cc	(revision 132203)
+++ chrome/common/chrome_paths.cc	(working copy)
@@ -71,6 +71,19 @@
     FILE_PATH_LITERAL("pepper/libppgoogletalk.so");
 
 #endif  // defined(OS_POSIX) && !defined(OS_MACOSX)
+
+#if defined(OS_LINUX)
+// The search path that contains information about per-extension
+// definition files.
+// /usr/share seems like a good choice, see: http://www.pathname.com/fhs/
+const char kFilepathSinglePrefExtensions[] =
+#if defined(GOOGLE_CHROME_BUILD)
+    FILE_PATH_LITERAL("/usr/share/google-chrome/extensions");
+#else
+    FILE_PATH_LITERAL("/usr/share/chromium/extensions");
+#endif
+#endif  // defined(OS_LINUX)
+
 }  // namespace
 
 namespace chrome {
@@ -364,6 +377,12 @@
       break;
     }
 #endif
+#if defined(OS_LINUX)
+    case chrome::DIR_SINGLE_EXTERNAL_EXTENSIONS: {
+      cur = FilePath(FILE_PATH_LITERAL(kFilepathSinglePrefExtensions));
+      break;
+    }
+#endif
     case chrome::DIR_EXTERNAL_EXTENSIONS:
 #if defined(OS_MACOSX)
       if (!chrome::GetGlobalApplicationSupportDirectory(&cur))