Extract CdmManager from MojoCdmService.

media/BUILD.gn

Index: media/BUILD.gn
diff --git a/media/BUILD.gn b/media/BUILD.gn
index 8d97ec513ba2e43f871c4a10b1db5d90b40fb9c7..e3608aca5c38589abb960673f354d86a17c967d6 100644
--- a/media/BUILD.gn
+++ b/media/BUILD.gn
@@ -377,10 +377,10 @@ component("media") {
   }
 
   if (disable_ffmpeg_video_decoders) {
-      sources -= [
-        "filters/decrypting_video_decoder.cc",
-        "filters/decrypting_video_decoder.h",
-      ]
+    sources -= [
+      "filters/decrypting_video_decoder.cc",
+      "filters/decrypting_video_decoder.h",
+    ]
   }
 
   if (is_android) {
@@ -516,6 +516,20 @@ component("media") {
   }
 }
 
+# Must not be a source_set() because CdmManager exposes a static singleton,
+# shared by multiple component()s.
+component("cdm_manager") {
+  sources = [
+    "cdm/cdm_manager.cc",
+    "cdm/cdm_manager.h",
+  ]
+  configs += [ ":media_implementation" ]

[xhwang, 2017/05/04 20:46:11]

Typically we only use this on the "media" target. Now, since we are depending on
"media", when we include a header file with MEDIA_EXPORT in "media", since we
have "media implementation", the MEDIA_EXPORT will be treated as "import"
instead of "export". I remember this will cause issues on some bots/platforms.

To avoid that, the right thing to do is to have a cdm_manager_export.h. It seems
overkill, but I don't know any better way to work around it.

[sandersd (OOO until July 31), 2017/05/04 21:03:35]

I have restricted the visibility and added a comment to explain this.

+  deps = [
+    ":media",
+    "//base",
+  ]
+}
+
 static_library("cdm_paths") {
   sources = [
     "cdm/cdm_paths.cc",
@@ -659,9 +673,7 @@ source_set("unit_tests") {
     ]
 
     if (!disable_ffmpeg_video_decoders) {
-      sources += [
-        "filters/ffmpeg_video_decoder_unittest.cc",
-      ]
+      sources += [ "filters/ffmpeg_video_decoder_unittest.cc" ]
     }
   }