Allow html5 videos to be played inline.

Enable inline video playback on iOS10 or greater.

BUG=395206

Review-Url: https://codereview.chromium.org/2265653002
Cr-Commit-Position: refs/heads/master@{#413457}

ios/web/web_state/ui/wk_web_view_configuration_provider.mm

@@ -71,6 +71,9 @@ WKWebViewConfigurationProvider::GetWebViewConfiguration() {
                                            WKDataDetectorTypePhoneNumber];
     }
 #endif
+    // API available on iOS 9, although doesn't appear to enable inline playback
+    // Works as intended on iOS 10+
+    [configuration_ setAllowsInlineMediaPlayback:YES];
     // setJavaScriptCanOpenWindowsAutomatically is required to support popups.
     [[configuration_ preferences] setJavaScriptCanOpenWindowsAutomatically:YES];
     [[configuration_ userContentController]