Rename buildflag_headers for consistency

This updates ppapi.

Targets go from foo_features to foo_buildflags
And similarly the header now has buildflags in the name.

BUG=814485
TEST=covered by build
[email protected]

Change-Id: I25f990ebd1e7f8530ddd0cee24dba31c88a45fae
Reviewed-on: https://chromium-review.googlesource.com/980921
Reviewed-by: Scott Violet <[email protected]>
Reviewed-by: Xiaohan Wang <[email protected]>
Reviewed-by: Daniel Cheng <[email protected]>
Commit-Queue: Scott Violet <[email protected]>
Cr-Commit-Position: refs/heads/master@{#546312}
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index 35f189b..6cbca29 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -11,7 +11,7 @@
 import("//gpu/vulkan/features.gni")
 import("//media/media_options.gni")
 import("//net/features.gni")
-import("//ppapi/features/features.gni")
+import("//ppapi/buildflags/buildflags.gni")
 import("//printing/features/features.gni")
 import("//third_party/WebKit/public/public_features.gni")
 import("//tools/ipc_fuzzer/ipc_fuzzer.gni")
@@ -115,7 +115,7 @@
     "//net",
     "//net:extras",
     "//net:http_server",
-    "//ppapi/features",
+    "//ppapi/buildflags",
     "//printing/features",
     "//services/audio:lib",
     "//services/audio/public/cpp",