Fix restoring of contexts in inlined finally code

Fix restoring of contexts in inlined finally code

When inlining code from a finally block before return or jump
instructions, do not restore the saved_try_context since the
inlined code is running in the context of the return or
jump instruction.

This is an old bug that surfaced in async code, since async code
deals with captured variables (contexts) much more than regular
code.

R=srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=44465

[hausner, 2015-03-12 20:48:28]

hausner@google.com changed reviewers:
+ iposva@google.com, srdjan@google.com

[srdjan, 2015-03-12 22:09:22]

LGTM

https://codereview.chromium.org/1006463003/diff/20001/runtime/vm/flow_graph_b...
File runtime/vm/flow_graph_builder.cc (right):

https://codereview.chromium.org/1006463003/diff/20001/runtime/vm/flow_graph_b...
runtime/vm/flow_graph_builder.cc:4295: 
Add a comment, similar to the on in CL, so that no one adds a
BuildRestoreContext accidentally.

[hausner, 2015-03-13 15:53:18]

Committed patchset #3 (id:40001) manually as r44465 (presubmit successful).

[regis, 2015-03-16 22:26:13]

regis@google.com changed reviewers:
+ regis@google.com

[regis, 2015-03-16 22:26:14]

DBC

https://codereview.chromium.org/1006463003/diff/40001/runtime/vm/flow_graph_b...
File runtime/vm/flow_graph_builder.cc (right):

https://codereview.chromium.org/1006463003/diff/40001/runtime/vm/flow_graph_b...
runtime/vm/flow_graph_builder.cc:4298: // that follows the inlined code. See
issue 22822.
at he -> at the

I find the comment implying a context mismatch somewhat misleading. The reason
we do not need to restore the context is that an inlined finally is never used
as an exception handler, therefore the context is always already set on entry.
In other words, the inlined finally block is never the target of a long jump
that would find an uninitialized current context variable.