Revert of device scale factor detection: use gtk-xft-dpi consistently

Revert of device scale factor detection: use gtk-xft-dpi consistently (patchset #6 id:100001 of https://codereview.chromium.org/1070433002/)

Reason for revert:
This patch makes content_shell segfault during startup.

Program received signal SIGSEGV, Segmentation fault.
0x00000000049d190a in views::DesktopScreenX11::BuildDisplaysFromXRandRInfo (this=0x35ed099f9200) at ../../ui/views/widget/desktop_aura/desktop_screen_x11.cc:291
291           views::LinuxUI::instance()->GetDeviceScaleFactor();
(gdb) bt
#0  0x00000000049d190a in views::DesktopScreenX11::BuildDisplaysFromXRandRInfo (this=0x35ed099f9200) at ../../ui/views/widget/desktop_aura/desktop_screen_x11.cc:291
#1  0x00000000049d096f in views::DesktopScreenX11::DesktopScreenX11 (this=0x35ed099f9200) at ../../ui/views/widget/desktop_aura/desktop_screen_x11.cc:107
#2  0x00000000049d1fab in views::CreateDesktopScreen () at ../../ui/views/widget/desktop_aura/desktop_screen_x11.cc:370
#3  0x0000000000451f28 in content::Shell::PlatformInitialize (default_window_size=...) at ../../content/shell/browser/shell_views.cc:421
#4  0x0000000000440158 in content::Shell::Initialize () at ../../content/shell/browser/shell.cc:146

Original issue's description:
> device scale factor detection: use gtk-xft-dpi consistently
>
> Before this CL, we used either gtk-xft-dpi (UI fonts) or the physical DPI of
> a more or less random display. This CL consistently uses gtk-xft-dpi which
> is the better alternative: users can directly influence it (by changing the
> Xft.dpi X resource, or via their gtkrc).
>
> See also https://github.com/derat/font-config-info for displaying your
> current system settings.
>
> BUG=473089, 143619
>
> Committed: https://crrev.com/06cda64742b45e1eb10bbbb66bca4b4da2efb3c9
> Cr-Commit-Position: refs/heads/master@{#324782}

TBR=sadrul@chromium.org,oshima@chromium.org,erg@google.com,erg@chromium.org,stapelberg@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=473089, 143619
Committed: https://crrev.com/5d03b6013e39b55de40a6789991f6240a79fd2f4
Cr-Commit-Position: refs/heads/master@{#324810}

[Timothy Loh, 2015-04-13 03:00:27]

Created Revert of device scale factor detection: use gtk-xft-dpi consistently

[commit-bot: I haz the power, 2015-04-13 03:00:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1079883002/1

[commit-bot: I haz the power, 2015-04-13 03:01:02]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-13 03:02:35]

Patchset 1 (id:??) landed as
https://crrev.com/5d03b6013e39b55de40a6789991f6240a79fd2f4
Cr-Commit-Position: refs/heads/master@{#324810}