BottomSheet keep padding

Before this change, the BottomSheet reset all paddings (except bottom)
to 0 when showing/hiding the keyboard. This irreversibly reset some
padding defined in XML.
Keep the existing padding for left, top, right and only set bottom to
a variable value.

Bug: b/152947599
Change-Id: I31cfec4bf8c8509ef39b1d0dbca0c5c7913b8db3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2141927Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Sandro Maggi <sandromaggi@google.com>
Cr-Commit-Position: refs/heads/master@{#757942}

chrome/android/java/src/org/chromium/chrome/browser/widget/bottomsheet/BottomSheet.java

@@ -313,7 +313,10 @@ class BottomSheet extends FrameLayout
                     // This shrinks the content size while retaining the default background color
                     // where the keyboard is appearing. If the sheet is not showing, resize the
                     // sheet to its default state.
-                    mBottomSheetContentContainer.setPadding(0, 0, 0, keyboardHeight);
+                    mBottomSheetContentContainer.setPadding(
+                            mBottomSheetContentContainer.getPaddingLeft(),
+                            mBottomSheetContentContainer.getPaddingTop(),
+                            mBottomSheetContentContainer.getPaddingRight(), keyboardHeight);
                 }
 
                 if (previousHeight != mContainerHeight