[Android] Add spellchecking support in android_webview.

android_webview/browser/aw_content_browser_client.cc

Index: android_webview/browser/aw_content_browser_client.cc
diff --git a/android_webview/browser/aw_content_browser_client.cc b/android_webview/browser/aw_content_browser_client.cc
index ff00820da9e4a0720f0027055df1956d60ff8487..33349367f110394501a126ede27233a16a42486b 100644
--- a/android_webview/browser/aw_content_browser_client.cc
+++ b/android_webview/browser/aw_content_browser_client.cc
@@ -33,6 +33,8 @@
 #include "components/cdm/browser/cdm_message_filter_android.h"
 #include "components/crash/content/browser/crash_micro_dump_manager_android.h"
 #include "components/navigation_interception/intercept_navigation_delegate.h"
+#include "components/spellcheck/browser/spellcheck_message_filter_platform.h"
+#include "components/spellcheck/common/spellcheck_switches.h"
 #include "content/public/browser/browser_message_filter.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/child_process_security_policy.h"
@@ -218,6 +220,13 @@ void AwContentBrowserClient::RenderProcessWillLaunch(
   host->AddFilter(new AwContentsMessageFilter(host->GetID()));
   host->AddFilter(new cdm::CdmMessageFilterAndroid());
   host->AddFilter(new AwPrintingMessageFilter(host->GetID()));
+
+#if defined(ENABLE_SPELLCHECK)
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+      spellcheck::switches::kEnableAndroidSpellChecker)) {
+    host->AddFilter(new SpellCheckMessageFilterPlatform(host->GetID()));
+  }
+#endif
 }
 
 bool AwContentBrowserClient::IsHandledURL(const GURL& url) {