Create ContentShellActivityTestRule and BaseJUnitRunner

TestRule(ContentShellActivityTestRule) in JUnit4 are the replacements for test base
classes (ContentShellTestBase) in JUnit3. ContentShellActivityTestRule and
ContentShellTestBase are refactored to use ContentShellTestCommon for implementation
of the utility method that tests uses. ContentShellPreconditionsTest and
ContentShellShellManagement are two tests converted to JUnit4 using
chromium-junit-migration script
(https://github.com/yoland68/chromium-junit-auto-migrate)

BaseJUnitRunner is the JUnit4 replacement for BaseChromiumInstrumentationTestRunner
for multidex support in devices lower than L

BUG=640116

Review-Url: https://codereview.chromium.org/2632043002
Cr-Commit-Position: refs/heads/master@{#454760}
12 files changed