In a recent CL (https://codereview.chromium.org/2738683003) I changed
the generation of call instructions on arm to emit a constant pool if
necessary. However it can happen now that a call is generated within a
PredictableSizeScope, which causes a crash if a constant pool is
actually emitted, which naturally changes the size of the generated
code. With this CL I add a flag to the generation of a call where we
can state explicitly that for particular calls, i.e. those calls within
a PredictableSizeScope, we do not want to emit a constant pool.

BUG=chromium:704528

Change-Id: I7740d5440d007a2a5457c524aa8eec1b74944d57
Reviewed-on: https://chromium-review.googlesource.com/459602Reviewed-by: Jacob Bramley <jacob.bramley@arm.com>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44181}