Add unit tests for CdmAdapter

media/BUILD.gn

Index: media/BUILD.gn
diff --git a/media/BUILD.gn b/media/BUILD.gn
index a7dac69db231e241b1248680e23ed30548866f8d..ef8bf9497898210f29ffb01fefcadf8c707d257e 100644
--- a/media/BUILD.gn
+++ b/media/BUILD.gn
@@ -658,7 +658,7 @@ test("media_unittests") {
     "test/data/",
   ]
 
-  # TODO(wolenetz): Fix size_t to int trunctaion in win64.
+  # TODO(wolenetz): Fix size_t to int truncation in win64.
   # See http://crbug.com/171009
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
@@ -695,6 +695,12 @@ test("media_unittests") {
     ]
   }
 
+  # If ExternalClearKey is built, we can test CdmAdapter.
+  if (enable_pepper_cdms) {
+    sources += [ "cdm/cdm_adapter_unittest.cc" ]
+    deps += [ "//media/cdm/ppapi:clearkeycdm" ]
+  }
+
   if (media_use_ffmpeg) {
     sources += [
       "ffmpeg/ffmpeg_common_unittest.cc",