[StartSurface] Keep AppBarLayout$ScrollingViewBehavior and $Behavior

Bug: 1017396
Change-Id: Ifad68f5fbd17b62aee6a34778bbe969638383eef
Binary-Size: Expected size increase because of AppBarLayout.
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1879770
Commit-Queue: Ganggui Tang <gogerald@chromium.org>
Reviewed-by: Sam Maier <smaier@chromium.org>
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709631}

chrome/android/features/start_surface/internal/BUILD.gn

@@ -123,4 +123,11 @@ android_library("java") {
   } else {
     java_files += [ "dummy/java/src/org/chromium/chrome/features/start_surface/ExploreSurfaceCoordinator.java" ]
   }
+
+  if (!is_java_debug) {
+    if (!defined(proguard_configs)) {
+      proguard_configs = []
+    }
+    proguard_configs += [ "proguard.flags" ]
+  }
 }

chrome/android/features/start_surface/internal/proguard.flags

+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# To fix crbug/1017396. This is because AppBarLayout$ScrollingViewBehavior
+# is instantiated via java.lang.reflect.Constructor in CoordinatorLayout.java.
+# Note that AppBarLayout$Behavior is needed to keep the scrolling behavior.
+-keep class android.support.design.widget.AppBarLayout$Behavior {
+    public <init>(android.content.Context, android.util.AttributeSet);
+    public <init>();
+}
+-keep class android.support.design.widget.AppBarLayout$ScrollingViewBehavior {
+    public <init>(android.content.Context, android.util.AttributeSet);
+    public <init>();
+}

chrome/android/java/monochrome_public_bundle.proguard_flags.expected

@@ -271,6 +271,25 @@
   @org.chromium.base.annotations.CheckDiscard *;
 }
 
+################################################################################
+# ../../chrome/android/features/start_surface/internal/proguard.flags
+################################################################################
+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# To fix crbug/1017396. This is because AppBarLayout$ScrollingViewBehavior
+# is instantiated via java.lang.reflect.Constructor in CoordinatorLayout.java.
+# Note that AppBarLayout$Behavior is needed to keep the scrolling behavior.
+-keep class android.support.design.widget.AppBarLayout$Behavior {
+    public <init>(android.content.Context, android.util.AttributeSet);
+    public <init>();
+}
+-keep class android.support.design.widget.AppBarLayout$ScrollingViewBehavior {
+    public <init>(android.content.Context, android.util.AttributeSet);
+    public <init>();
+}
+
 ################################################################################
 # ../../chrome/android/java/proguard.flags
 ################################################################################