Add support for component=shared_library for base_unittests.

icu.isolate

Index: icu.isolate
diff --git a/icu.isolate b/icu.isolate
index b106ccc2c88dcbf8b87854e4826dd33044cd5135..35b60bd3fe28d3f05e7bf4ab597b551f5ecf356a 100644
--- a/icu.isolate
+++ b/icu.isolate
@@ -20,5 +20,29 @@
         ],
       },
     }],
+    ['OS=="linux" and component=="shared_library"', {
+      'variables': {
+        'isolate_dependency_tracked': [
+          '<(PRODUCT_DIR)/lib/libicui18n.so',
+          '<(PRODUCT_DIR)/lib/libicuuc.so',
+        ],
+      },
+    }],
+    ['OS=="mac" and component=="shared_library"', {
+      'variables': {
+        'isolate_dependency_tracked': [
+          '<(PRODUCT_DIR)/libicui18n.dylib',
+          '<(PRODUCT_DIR)/libicuuc.dylib',
+        ],
+      },
+    }],
+    ['OS=="win" and component=="shared_library"', {
+      'variables': {
+        'isolate_dependency_tracked': [
+          '<(PRODUCT_DIR)/icui18n.dll',
+          '<(PRODUCT_DIR)/icuuc.dll',
+        ],
+      },
+    }],
   ],
 }