Add missing P check in webview data dir code.

The call to WebViewDelegate.getDataDirectorySuffix() was missing an API
level check and only working correctly because the upstream version of
the class was a stub that returned null - this broke non-P devices after
upstreaming.

Bug: 857066
Change-Id: I43e790e3b5ab9f8e26b35fa15c753ab0782a4342
Reviewed-on: https://chromium-review.googlesource.com/1117027Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Commit-Queue: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570812}

android_webview/glue/java/src/com/android/webview/chromium/WebViewChromiumFactoryProvider.java

@@ -264,7 +264,11 @@ public class WebViewChromiumFactoryProvider implements WebViewFactoryProvider {
 
             try (ScopedSysTraceEvent e2 = ScopedSysTraceEvent.scoped(
                          "WebViewChromiumFactoryProvider.loadChromiumLibrary")) {
-                AwBrowserProcess.loadLibrary(mWebViewDelegate.getDataDirectorySuffix());
+                String dataDirectorySuffix = null;
+                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+                    dataDirectorySuffix = mWebViewDelegate.getDataDirectorySuffix();
+                }
+                AwBrowserProcess.loadLibrary(dataDirectorySuffix);
             }
 
             try (ScopedSysTraceEvent e2 = ScopedSysTraceEvent.scoped(