[Merge to M60] Respect GDK_SCALE and GDK_DPI_SCALE when calculating scale factor

[Merge to M60] Respect GDK_SCALE and GDK_DPI_SCALE when calculating scale factor

> This CL is a followup to [1] which used 'gdk-window-scaling-factor'
> and 'gdk-unscaled-dpi' to calculate the scaling factor.  I intentially
> avoided using the GdkScreen API for this since the required functions
> were added in version 3.9.10, and opted to get the settings directly.
> This doesn't work all the time though, because GTK allows overriding
> these settings with the GDK_SCALE and GDK_DPI_SCALE environment
> variables (but only when using the X11 backend).
>
> This CL makes the change to use those functions, at the cost of
> bumping the required GTK dep from 3.3.16 to 3.9.10 (the oldest distro
> we support, Trusty, has 3.10.8).
>
> As a bonus, GdkScreen has a separate scale factor per monitor, so we
> can finally stop using the global scale factor for all monitors.
>
> [1] https://codereview.chromium.org/2899943002/
>
> BUG=730757, 732440
> R=erg@chromium.org,thestig@chromium.org
> CC=oshima@chromium.org
>
> Review-Url: https://codereview.chromium.org/2937623006
> Cr-Commit-Position: refs/heads/master@{#480167}

BUG=732440
TBR=erg@chromium.org,thestig@chromium.org
CC=oshima@chromium.org
NOTRY=true
NOPRESUBMIT=true
NOTREECHECKS=true

Review-Url: https://codereview.chromium.org/2961473002
Cr-Commit-Position: refs/branch-heads/3112@{#454}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
Committed: https://chromium.googlesource.com/chromium/src/+/8d1845c2267b05df565fa33e3c5e2b0e242a21cc

[Tom Anderson, 2017-06-23 21:42:10]

The CQ bit was checked by thomasanderson@chromium.org

[commit-bot: I haz the power, 2017-06-23 21:42:35]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-06-23 21:43:00]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1498254130294030, "parent_rev":
"2c003ddd2dfa6f0605ba5a3f949e3558f7f15447", "commit_rev":
"8d1845c2267b05df565fa33e3c5e2b0e242a21cc"}

[commit-bot: I haz the power, 2017-06-23 21:43:16]

Description was changed from

==========
[Merge to M60] Respect GDK_SCALE and GDK_DPI_SCALE when calculating scale factor

> This CL is a followup to [1] which used 'gdk-window-scaling-factor'
> and 'gdk-unscaled-dpi' to calculate the scaling factor.  I intentially
> avoided using the GdkScreen API for this since the required functions
> were added in version 3.9.10, and opted to get the settings directly.
> This doesn't work all the time though, because GTK allows overriding
> these settings with the GDK_SCALE and GDK_DPI_SCALE environment
> variables (but only when using the X11 backend).
>
> This CL makes the change to use those functions, at the cost of
> bumping the required GTK dep from 3.3.16 to 3.9.10 (the oldest distro
> we support, Trusty, has 3.10.8).
>
> As a bonus, GdkScreen has a separate scale factor per monitor, so we
> can finally stop using the global scale factor for all monitors.
>
> [1] https://codereview.chromium.org/2899943002/
>
> BUG=730757,732440
> R=erg@chromium.org,thestig@chromium.org
> CC=oshima@chromium.org
>
> Review-Url: https://codereview.chromium.org/2937623006
> Cr-Commit-Position: refs/heads/master@{#480167}

BUG=732440
TBR=erg@chromium.org,thestig@chromium.org
CC=oshima@chromium.org
NOTRY=true
NOPRESUBMIT=true
NOTREECHECKS=true
==========

to

==========
[Merge to M60] Respect GDK_SCALE and GDK_DPI_SCALE when calculating scale factor

> This CL is a followup to [1] which used 'gdk-window-scaling-factor'
> and 'gdk-unscaled-dpi' to calculate the scaling factor.  I intentially
> avoided using the GdkScreen API for this since the required functions
> were added in version 3.9.10, and opted to get the settings directly.
> This doesn't work all the time though, because GTK allows overriding
> these settings with the GDK_SCALE and GDK_DPI_SCALE environment
> variables (but only when using the X11 backend).
>
> This CL makes the change to use those functions, at the cost of
> bumping the required GTK dep from 3.3.16 to 3.9.10 (the oldest distro
> we support, Trusty, has 3.10.8).
>
> As a bonus, GdkScreen has a separate scale factor per monitor, so we
> can finally stop using the global scale factor for all monitors.
>
> [1] https://codereview.chromium.org/2899943002/
>
> BUG=730757,732440
> R=erg@chromium.org,thestig@chromium.org
> CC=oshima@chromium.org
>
> Review-Url: https://codereview.chromium.org/2937623006
> Cr-Commit-Position: refs/heads/master@{#480167}

BUG=732440
TBR=erg@chromium.org,thestig@chromium.org
CC=oshima@chromium.org
NOTRY=true
NOPRESUBMIT=true
NOTREECHECKS=true

Review-Url: https://codereview.chromium.org/2961473002
Cr-Commit-Position: refs/branch-heads/3112@{#454}
Cr-Branched-From:
b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
Committed:
https://chromium.googlesource.com/chromium/src/+/8d1845c2267b05df565fa33e3c5e...
==========

[commit-bot: I haz the power, 2017-06-23 21:43:17]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/8d1845c2267b05df565fa33e3c5e...