android: Remove in-process sync compositor code path

Remove the merge thread path. Also remove kIPCSyncCompositing
and replace it with an android-only method on ContentClient.

BUG=526842

Review URL: https://codereview.chromium.org/1838853005

Cr-Commit-Position: refs/heads/master@{#388428}

android_webview/common/aw_content_client.cc

@@ -73,4 +73,8 @@ void AwContentClient::SetGpuInfo(const gpu::GPUInfo& gpu_info) {
                   [](char c) { return !::isprint(c); }, '_');
 }
 
+bool AwContentClient::UsingSynchronousCompositing() {
+  return true;
+}
+
 }  // namespace android_webview

android_webview/common/aw_content_client.h

@@ -30,8 +30,9 @@ class AwContentClient : public content::ContentClient {
       int resource_id,
       ui::ScaleFactor scale_factor) const override;
   bool CanSendWhileSwappedOut(const IPC::Message* message) override;
-
   void SetGpuInfo(const gpu::GPUInfo& gpu_info) override;
+  bool UsingSynchronousCompositing() override;
+
   const std::string& gpu_fingerprint() const { return gpu_fingerprint_; }
 
  private:

android_webview/javatests/src/org/chromium/android_webview/test/AwContentsTest.java

@@ -35,7 +35,6 @@
 import org.chromium.content.browser.ChildProcessConnection;
 import org.chromium.content.browser.ChildProcessLauncher;
 import org.chromium.content.browser.test.util.CallbackHelper;
-import org.chromium.content.common.ContentSwitches;
 import org.chromium.content_public.browser.AccessibilitySnapshotCallback;
 import org.chromium.content_public.browser.AccessibilitySnapshotNode;
 import org.chromium.net.test.util.TestWebServer;
@@ -594,9 +593,7 @@ public void releaseAllModerateBindings() {}
      */
     @Feature({"AndroidWebView"})
     @SmallTest
-    @CommandLineFlags.Add({
-            AwSwitches.WEBVIEW_SANDBOXED_RENDERER,
-            ContentSwitches.IPC_SYNC_COMPOSITING})
+    @CommandLineFlags.Add(AwSwitches.WEBVIEW_SANDBOXED_RENDERER)
     @ParameterizedTest.Set
     public void testSandboxedRendererWorks() throws Throwable {
         MockBindingManager bindingManager = new MockBindingManager();

android_webview/javatests/src/org/chromium/android_webview/test/AwTestBase.java

@@ -31,7 +31,6 @@
 import org.chromium.content.browser.test.util.Criteria;
 import org.chromium.content.browser.test.util.CriteriaHelper;
 import org.chromium.content.browser.test.util.TestCallbackHelperContainer.OnPageFinishedHelper;
-import org.chromium.content.common.ContentSwitches;
 import org.chromium.content_public.browser.LoadUrlParams;
 import org.chromium.net.test.util.TestWebServer;
 
@@ -63,8 +62,7 @@
                                 arguments = {
                                     @Parameter.Argument(
                                         name = CommandLineFlags.Parameter.ADD_ARG,
-                                        stringArray = {AwSwitches.WEBVIEW_SANDBOXED_RENDERER,
-                                                ContentSwitches.IPC_SYNC_COMPOSITING})
+                                        stringArray = {AwSwitches.WEBVIEW_SANDBOXED_RENDERER})
             })})})
 public class AwTestBase
         extends BaseActivityInstrumentationTestCase<AwTestRunnerActivity> {

android_webview/lib/main/aw_main_delegate.cc

@@ -72,7 +72,6 @@ bool AwMainDelegate::BasicStartupComplete(int* exit_code) {
       ->set_fling_touchscreen_tap_suppression_enabled(false);
 
   base::CommandLine* cl = base::CommandLine::ForCurrentProcess();
-  cl->AppendSwitch(switches::kIPCSyncCompositing);
   cl->AppendSwitch(cc::switches::kEnableBeginFrameScheduling);
 
   // WebView uses the Android system's scrollbars and overscroll glow.