HANG browser_tests

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on June 13, 2014 14:03:33_

Many browser_tests have been hanging on the bots. An example is
CalculatorBrowserTest.Model which I'm focusing on here as I can reproduce
it locally.

Hangs with full mode, and also with -leaks_only -no_count_leaks:
% BROWSER_WRAPPER="d:\derek\drmemory\git\build_x86_dbg\bin\drmemory.exe $DRMEM_CHROME_ARGS -leaks_only -no_count_leaks -pause_at_assert -logdir C:/users/derek/AppData/LocalLow/drmemory -dr d:/derek/dr/git/exports --" ./browser_tests --ui-test-action-timeout=1200000 --ui-test-action-max-timeout=2800000 --ui-test-terminate-timeout=1200000 --no-sandbox --gtest_filter=CalculatorBrowserTest.Model

In full mode in windbg: no DR or DrMem on any callstack.

Plain DR release build works:
% BROWSER_WRAPPER="d:\derek\dr\git\exports\bin32\drrun.exe -logdir C:/users/derek/AppData/LocalLow/drmemory --" ./browser_tests --ui-test-action-timeout=1200000 --ui-test-action-max-timeout=2800000 --ui-test-terminate-timeout=1200000 --no-sandbox --gtest_filter=CalculatorBrowserTest.Model
[ OK ] CalculatorBrowserTest.Model (8897 ms)

Debug DR also works:
[ OK ] CalculatorBrowserTest.Model (143719 ms)

With a client that uses kernel32.dll:
-c d:/derek/dr/git/build_x86_dbg_tests/api/samples/bin/bbcount.dll
[ OK ] CalculatorBrowserTest.Model (17731 ms)

With instrcalls client that uses drsyms (modified to be low-overhead: just
looks up symbol inside dead code in bb event, w/ clean calls removed)
-c d:/derek/dr/git/build_x86_dbg_tests/api/samples/bin/instrcalls.dll
[ OK ] CalculatorBrowserTest.Model (11705 ms)

So this seems to be specific to Dr. Memory? It may still be a DR
isolation bug though but filing in DrMem tracker until that's proven.

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=1564_