debugger: Make settings widget resizeable

The settings widget was laid out by hand, eg. the widths of most
elements were hardcoded. This prevented it from being laid out by the Qt
widget system. This in turn prevents the widget from shrinking to its
optimal size. This in turn causes cascading effect where the geometry of
many of the UI widgets has to be hard-coded. This in turn prevents
proper resizing of the UI.

Make Qt layout the settings widget by following changes:

a) Group settings in QGroupBox groups instead of hand-written
layouts and labels hardcoded in certain places.

b) Remove "Expanding" size policy from settings widget. The widget
calculates its own size based on the widgets inside. Thus "Preferred"
is the correct policy to use, as expanding the widget will not
bring any new content visible.

c) Remove maximum width 250 from Settings widget

d) Make "canvas settings and image layout", eg. the horizontal layout
holding the settings widget divide the space between the picture and
settings like so: settings uses up only as much as it needs (stretch
factor 0), while picture uses up everything else (stretch factor 1).

In order to do a) reasonably, reorganize the UI and the code a bit:

a1) Rename settings group "visual filter" to "Visualizations".
a2) Make "visual filter: on/off" combo box a checkbox in
"Visualizations".
a3) Move "Mega viz" setting checkbox from "raster" (or "render targets")
section to "Visualizations"
a4) Move "PathOps" setting checkbox from "raster" to "Visualizations"

a5) Make Raster and GL checkboxes use QGroupBox checkbox feature

a6) Move "current command", "command hitbox" and "zoom level" from
"Settings" widget to part of "Inspector" concept. These pieces of
information are now visualized as their own box in the right-hand
bar, below settings.

a7) Do not expose settings user selects through the UI widgets
state that record the user interacts with. Instead, expose it as state
of the "settings widget". Thus settings widget provides "raster settings
changed" signal, which the client hook to and then query the state
through the object API.

This makes the full window a bit shorter.

This commit is part of work that tries to make the
debugger window to be a bit more resizeable, so that it would fit
1900x1200 screen.

Review URL: https://codereview.chromium.org/829933002
debugger: Make draw command image widget resize

Make draw command image widget resize. The widget was not resizing,
effectively preventing the window from being resized smaller.

Make the rasterized draw command image be proportional to the widget
size. The draw rasterization canvas is still an equilateral rectangle
with dimensions of the smaller side of the widget.

Makes the widget re-rasterize the image only when the draw command
changes, not for each widget paint.

Renames the widget from "image widget" to "draw command geometry
widget".

Makes the background of the image black, similar to the raster widget
background.

Adds a tooltip saying "Command geometry" for the widget, so that user might
understand what the contents should be.

This commit is part of work that tries to make the debugger window to be
a bit more resizeable, so that it would fit 1900x1200 screen.

Review URL: https://codereview.chromium.org/787143004
Update SKP version

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Review URL: https://codereview.chromium.org/805813006