Set aspect ratio 1:1 if there is no screenshot

Right now, we use a fixed size for this, which doesn't scale well
to multiple devices with different screen aspect ratios. A more elegant
fix is to keep the aspect ratio if we don't have a screenshot.

BUG=947638

Change-Id: I7ef1465d684fe73c67c1ba37e00511281e3635b8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1546628Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Yusuf Ozuysal <yusufo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#646519}

chrome/android/features/tab_ui/java/src/org/chromium/chrome/browser/tasks/tab_management/SilenceLintErrors.java

@@ -28,7 +28,8 @@ import org.chromium.chrome.R;
                     R.layout.bottom_tab_strip_toolbar, R.drawable.tabstrip_selected,
                     R.dimen.tab_list_card_padding, R.dimen.tab_list_mini_card_text_size,
                     R.dimen.tab_list_mini_card_frame_size, R.dimen.tab_list_mini_card_radius,
-                    R.drawable.tabstrip_favicon_background, R.dimen.swipe_to_dismiss_threshold};
+                    R.drawable.tabstrip_favicon_background, R.dimen.swipe_to_dismiss_threshold,
+                    R.dimen.tab_grid_thumbnail_card_default_size};
 
     private SilenceLintErrors() {}
 }

chrome/android/features/tab_ui/java/src/org/chromium/chrome/browser/tasks/tab_management/TabGridViewBinder.java

@@ -66,6 +66,7 @@ class TabGridViewBinder {
             Callback<Bitmap> callback = result -> {
                 if (result == null) {
                     holder.thumbnail.setImageResource(0);
+                    holder.thumbnail.setMinimumHeight(holder.thumbnail.getWidth());
                 } else {
                     holder.thumbnail.setImageBitmap(result);
                 }

chrome/android/java/res/layout/tab_grid_card_item.xml

@@ -38,7 +38,6 @@
                 android:id="@+id/tab_thumbnail"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
-                android:minHeight="@dimen/tab_grid_thumbnail_card_default_size"
                 android:layout_below="@id/tab_title"
                 android:gravity="center_horizontal"
                 android:adjustViewBounds="true"