[ios] Improves the InfobarModal height calculation.

- Removes fixed height padding.
- Adds the navigation bar height to the Modal height. Renames
infobarModalContentHeight to infobarModalHeight to reflect this.


TBR=sczs@chromium.org

(cherry picked from commit 5de0ee99edf98bd3cb11d73fe081d38096a0ad17)

Bug: 973229
Change-Id: I668794957dc5eb1690481c7c65c3f810c75380e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1657228
Reviewed-by: Chris Lu <thegreenfrog@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#668857}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1663178
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/branch-heads/3809@{#416}
Cr-Branched-From: d82dec1a818f378c464ba307ddd9c92133eac355-refs/heads/master@{#665002}

• ios/chrome/browser/ui/infobars/coordinators/infobar_confirm_coordinator.mm[diff]
• ios/chrome/browser/ui/infobars/coordinators/infobar_coordinator.mm[diff]
• ios/chrome/browser/ui/infobars/coordinators/infobar_coordinator_implementation.h[diff]
• ios/chrome/browser/ui/infobars/coordinators/infobar_password_coordinator.mm[diff]
• ios/chrome/browser/ui/infobars/presentation/infobar_modal_presentation_controller.mm[diff]