Autoplay: Add WebAudio flag to chrome://flags

Add the "AutoplayIgnoresWebAudio" flag to chrome://flags
so users can control it.

BUG=841933

Change-Id: Iee045d7a14b6e169c686588adc6ba11ce40dc095
Reviewed-on: https://chromium-review.googlesource.com/1074195
Reviewed-by: Jochen Eisinger <[email protected]>
Commit-Queue: Becca Hughes <[email protected]>
Cr-Commit-Position: refs/heads/master@{#562466}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index e83aa43..a2fb5fb8 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -250,6 +250,9 @@
 extern const char kEnableAutofillSendExperimentIdsInPaymentsRPCsName[];
 extern const char kEnableAutofillSendExperimentIdsInPaymentsRPCsDescription[];
 
+extern const char kEnableAutoplayIgnoreWebAudioName[];
+extern const char kEnableAutoplayIgnoreWebAudioDescription[];
+
 extern const char kEnableBreakingNewsPushName[];
 extern const char kEnableBreakingNewsPushDescription[];