Add a gyp flag to allow use of the system's version of libexpat

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 401ceb298b4bf22f978b2019300220f0747dd898..b076e610045136e184708f3348bcd6cbcbd3c78e 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -942,13 +942,13 @@
           }],
         ],
         # TODO(steveblock): Investigate using the system versions of sqlite,
-        # libjpeg, expat and stlport.
+        # libjpeg and stlport.
         # Enable to use system sqlite.
         'use_system_sqlite%': 0,  # '<(android_build_type)',
         # Enable to use system libjpeg.
         'use_system_libjpeg%': 0,  # '<(android_build_type)',
-        # Enable to use the system libexpat.
-        'use_system_libexpat%': 0,  # '<(android_build_type)',
+        # Enable to use the system expat.
+        'use_system_expat%': '<(android_build_type)',

[Lei Zhang, 2012/07/09 23:05:33]

Is |android_build_type| ever going to be non-zero? I don't know the future plans
for this variable.

         # Enable to use the system stlport, otherwise statically
         # link the NDK one?
         'use_system_stlport%': 0,  # '<(android_build_type)',