Prepare for ISO-8859-1 to windows-1252 switch

The following Blink CL will make 'windows-1252' the canonical name
for 'ISO-8859-1', 'US-ASCII' and 'windows-1252'. All three will be
treated synonymously per the WHATWG Encoding spec.

   https://codereview.chromium.org/655083002/

We have some test results with 'ISO-8859-1'. Change them to use
windows-1252 and disable them before landing the above Blink CL.

For PrefsTabHelperBrowserTest.WebPrefs, I made the test more robust
by setting 'windows-1251' (not '1252') as the default charset in
the Test Preference file.

Once the Blink CL is landed and rolled, we'll re-enable the disabled
tests as a part of the following Cr CL:
  https://codereview.chromium.org/649413002/ ,
which rolls ICU 52 to the latest revision (the other side of
ISO-8859-1 to windows-1252 transition).

TBR=jochen,rdsmith,mnissler,jsbell
BUG=412053
TEST=browser_tests the following tests (before and after the Blink roll)
    BrowserEncodingTest.TestEncodingAutoDetect
    BrowserEncodingTest.TestOverrideEncoding
    EncodingAliases/BrowserEncodingTest.TestEncodingAliasMapping
    SavePageBrowserTest.FileNameFromPageTitle
    SavePageBrowserTest.SaveCompleteHTML
    PrefsTabHelperBrowserTest.WebPrefs

Review URL: https://codereview.chromium.org/643993004

Cr-Commit-Position: refs/heads/master@{#300069}
4 files changed