AOSP/UnifiedEmail - bug fix to composing messages.

As part of porting https://critique.corp.google.com/#review/247540041,
needed to make EXTRA_TO, EXTRA_CC, EXTRA_BCC, EXTRA_SUBJECT, EXTRA_BODY
public so that they couuld be accessed from packages/apps/Email package.

Bug: 127320867

Test: manual - Ran the following tests on Pixel phone. Tested the email UI.

$ make -j 40
  -rw-r--r-- 1 rtenneti primarygroup 6375626 May  5 19:49 out/target/product/marlin/system/product/app/Email/Email.apk

$ make UnifiedEmailTests -j
  -rw-r--r-- 1 rtenneti primarygroup 311703 May  5 20:04 out/target/product/marlin/testcases/UnifiedEmailTests/arm64/UnifiedEmailTests.apk

$ make EmailTests -j
  -rw-r--r-- 1 rtenneti primarygroup 365023 May 13 14:39 out/target/product/marlin/testcases/EmailTests/arm64/EmailTests.apk

$ adb install -r out/target/product/marlin/system/product/app/Email/Email.apk
$ adb install -r out/target/product/marlin/testcases/EmailTests/arm64/EmailTests.apk
$ adb install -r out/target/product/marlin/testcases/UnifiedEmailTests/arm64/UnifiedEmailTests.apk

$ adb shell am instrument -w com.android.mail.emailtests
  Time: 3.519
  OK (157 tests)

Change-Id: I2a0e1048bac20c4346ec16d4bc8151297971fe0d
Merged-In: I2a0e1048bac20c4346ec16d4bc8151297971fe0d
1 file changed