[Android] Prevent division by zero in Bottom Sheet

If the state changes while or briefly after the bottom sheet is hidden,
the BottomSheet#sendOffsetChangeEvents triggers without sheet content
which sets the maximum full ratio to 0.
Since the hidden full ration is divided by that maximum full ration, the
result is NaN which is then propagated to Observers [1].

[1] Sample stack trace of an Observer receiving NaN after onLayout:
BottomContainer${EmptyBottomSheetObserver}#onSheetOffsetChanged(NaN, 0);
        at Rz1.a(PG:2)
        at org.chromium.chrome.browser.widget.bottomsheet.BottomSheet.a(PG:102)
        at org.chromium.chrome.browser.widget.bottomsheet.BottomSheet.a(PG:127)
        at TV1.onLayoutChange(PG:40)
        at android.view.View.layout(View.java:19677)
        at android.view.ViewGroup.layout(ViewGroup.java:6075)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)

Bug: 1021885
Change-Id: I21573d91b92f1c017ec2267381c196ae79903545
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1901566Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Friedrich [CET] <fhorschig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713381}

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

@@ -927,8 +927,10 @@ public class BottomSheet
                 mContainerHeight > 0 ? offsetWithBrowserControls / (float) mContainerHeight : 0;
 
         // This ratio is relative to the peek and full positions of the sheet.
-        float hiddenFullRatio = MathUtils.clamp(
-                (screenRatio - getHiddenRatio()) / (getFullRatio() - getHiddenRatio()), 0, 1);
+        float maxHiddenFullRatio = getFullRatio() - getHiddenRatio();
+        float hiddenFullRatio = maxHiddenFullRatio == 0
+                ? 0
+                : MathUtils.clamp((screenRatio - getHiddenRatio()) / maxHiddenFullRatio, 0, 1);
 
         if (offsetWithBrowserControls < getSheetHeightForState(SheetState.HIDDEN)) {
             mLastOffsetRatioSent = 0;