Bug 1487113 - Add pref javascript.options.wasm_caching. r=necko-reviewers,valentin

Differential Revision: https://phabricator.services.mozilla.com/D27101

dom/fetch/FetchDriver.cpp

@@ -42,6 +42,7 @@
 #include "mozilla/StaticPrefs_browser.h"
 #include "mozilla/StaticPrefs_network.h"
 #include "mozilla/StaticPrefs_privacy.h"
+#include "mozilla/StaticPrefs_javascript.h"
 #include "mozilla/Unused.h"
 
 #include "Fetch.h"
@@ -826,7 +827,7 @@ nsresult FetchDriver::HttpFetch(
     if (mRequest->GetIntegrity().IsEmpty()) {
       MOZ_ASSERT(!FetchUtil::WasmAltDataType.IsEmpty());
       nsCOMPtr<nsICacheInfoChannel> cic = do_QueryInterface(chan);
-      if (cic) {
+      if (cic && StaticPrefs::javascript_options_wasm_caching()) {
         cic->PreferAlternativeDataType(
             FetchUtil::WasmAltDataType, nsLiteralCString(WASM_CONTENT_TYPE),
             nsICacheInfoChannel::PreferredAlternativeDataDeliveryType::

modules/libpref/init/StaticPrefList.yaml

@@ -6026,6 +6026,11 @@
     value: true
     mirror: always
 
+- name: javascript.options.wasm_caching
+  type: bool
+  value: true
+  mirror: always
+
 # The amount of time we wait between a request to GC (due to leaving a page) and doing the actual GC, in ms.
 - name: javascript.options.gc_delay
   type: uint32_t