[Chromium] Let the embedder override the max page scale factor set by the page

[Chromium] Let the embedder override the max page scale factor set by the page
https://bugs.webkit.org/show_bug.cgi?id=89406

Reviewed by James Robinson.

Chrome on Android has an option to force the web site to allow page
scaling (for accessibility). This patch adds
WebView::setIgnoreViewportTagMaximumScale, which instructs the WebView
to ignore the maximum scale factor supplied by by the page in the
viewport meta tag.

This patch is a bit different from how this is implemented on the
chromium-android branch, but I'll clean up the branch once this patch
lands.

* public/WebView.h:
(WebView):
* src/ChromeClientImpl.cpp:
(WebKit::ChromeClientImpl::dispatchViewportPropertiesDidChange):
* src/WebViewImpl.cpp:
(WebKit::WebViewImpl::WebViewImpl):
(WebKit::WebViewImpl::setIgnoreViewportTagMaximumScale):
(WebKit):
* src/WebViewImpl.h:
(WebViewImpl):
(WebKit::WebViewImpl::ignoreViewportTagMaximumScale):
* tests/WebFrameTest.cpp:
(WebKit::TEST_F):
(WebKit):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121213 268f45cc-cd09-0410-ab3c-d52691b4dbfc