Update chromiumcontent/BUILD.gn for Chromium 67

media: Remove widevinecdmadapter target
https://chromium-review.googlesource.com/957868

Rename buildflag_headers for consistency
https://chromium-review.googlesource.com/975990

The Great Blink mv for source files, part 2.
https://chromium-review.googlesource.com/1001153

chromiumcontent/BUILD.gn

@@ -471,7 +471,7 @@ component("pepper_flash") {
   deps = [
     "//content/public/browser",
     "//content/public/renderer",
-    "//media:media_features",
+    "//media:media_buildflags",
     "//ppapi/host",
     "//ppapi/proxy",
     "//ppapi/proxy:ipc",