[ExpandablePaymentHandler] Set full height to be 90%

Context:
The full state of the Expandable Payment Handler should leave some room
above the sheet, in order for users to see the main tab's toolbar.

Before change:
The height of the full state of the PH bottomsheet covers the whole
tab.

After change:
The height of the full state of the PH bottomsheet occupies 90% of
the tab height.


Bug: 1052158

Change-Id: Id683da48a10119e97a935aabf7dc06ed5a6b69bf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2058909Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Commit-Queue: Liquan (Max) Gu <maxlg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742211}

chrome/android/java/src/org/chromium/chrome/browser/payments/handler/PaymentHandlerView.java

@@ -103,6 +103,11 @@ import org.chromium.ui.base.ActivityWindowAndroid;
         return mToolbarView;
     }
 
+    @Override
+    public float getFullHeightRatio() {
+        return 0.9f;
+    }
+
     @Override
     public boolean hasCustomScrimLifecycle() {
         return true;