media: Replace WIDEVINE_CDM_AVAILABLE with ENABLE_WIDEVINE buildflag

- Add ENABLE_WIDEVINE buildflag
- Check BUILDFLAG(ENABLE_WIDEVINE) instead of
  defined(WIDEVINE_CDM_AVAILABLE)
- Since WIDEVINE_CDM_AVAILABLE is not needed, remove a lot of
  dependencies on widevine_cdm_version.h
- widevine_cdm_version.h is still needed to get
  WIDEVINE_CDM_VERSION_STRING and WIDEVINE_CDM_MIN_GLIBC_VERSION.
- Some BUILD.gn cleanup to use "enable_widevine". Previously this wasn't
  possible since WIDEVINE_CDM_AVAILABLE is a define.
- Remove third_party/widevine/cdm/stub/, whose sole purpose was to define
  WIDEVINE_CDM_AVAILABLE when "enable_widevine" is enabled.

Bug: 349182
Test: No functionality change
Change-Id: I864963033c4ae3a61b4ebde14c6bb68ed18e88f0
Reviewed-on: https://chromium-review.googlesource.com/1239873
Reviewed-by: John Rummell <[email protected]>
Reviewed-by: Lei Zhang <[email protected]>
Reviewed-by: Luke Halliwell <[email protected]>
Commit-Queue: Xiaohan Wang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#594602}
diff --git a/components/cdm/renderer/BUILD.gn b/components/cdm/renderer/BUILD.gn
index cbf8471..c8e6160f 100644
--- a/components/cdm/renderer/BUILD.gn
+++ b/components/cdm/renderer/BUILD.gn
@@ -3,13 +3,20 @@
 # found in the LICENSE file.
 
 import("//build/config/jumbo.gni")
+import("//third_party/widevine/cdm/widevine.gni")
 
 jumbo_static_library("renderer") {
   sources = [
     "external_clear_key_key_system_properties.cc",
     "external_clear_key_key_system_properties.h",
-    "widevine_key_system_properties.cc",
-    "widevine_key_system_properties.h",
+  ]
+  deps = [
+    "//base",
+    "//components/cdm/common",
+    "//content/public/renderer",
+    "//media",
+    "//media:media_buildflags",
+    "//third_party/widevine/cdm:buildflags",
   ]
 
   if (is_android) {
@@ -19,12 +26,11 @@
     ]
   }
 
-  deps = [
-    "//base",
-    "//components/cdm/common",
-    "//content/public/renderer",
-    "//media",
-    "//media:media_buildflags",
-    "//third_party/widevine/cdm:headers",
-  ]
+  if (enable_widevine) {
+    sources += [
+      "widevine_key_system_properties.cc",
+      "widevine_key_system_properties.h",
+    ]
+    deps += [ "//third_party/widevine/cdm:headers" ]
+  }
 }