Support generating English strings.xml files in android2grd.
Support generating English strings.xml files in android2grd.

English needs to be treated differently:
 - There is no xtb file containing English translations
 - The output file is values/strings.xml, not values-en/strings.xml

Review URL: https://codereview.chromium.org/11742035

git-svn-id: 50c90c531a9fd8f38831f054b7ea6b96f50d91dc@100 7262f16d-afe8-6277-6482-052fa10e57b1

geekboxzone/lollipop_external_chromium_org_tools_grit,MIPS/external-chromium_org-tools-grit,xin3liang/platform_external_chromium_org_tools_grit,IllusionRom-deprecated/android_platform_external_chromium_org_tools_grit,android-ia/platform_external_chromium_org_tools_grit,yinquan529/platform-external-chromium_org-tools-grit,bpsinc-native/src_tools_grit,android-ia/platform_external_chromium_org_tools_grit,yinquan529/platform-external-chromium_org-tools-grit,bpsinc-native/src_tools_grit,Omegaphora/external_chromium_org_tools_grit,AOSPU/external_chromium_org_tools_grit,Omegaphora/external_chromium_org_tools_grit,geekboxzone/lollipop_external_chromium_org_tools_grit