Fix chrome_messages_json generator to handle <if> properly.
Fix chrome_messages_json generator to handle <if> properly.

Previously chrome_messages_json formatter wasn't handling <if> properly -
it was putting all messages to the generated files, even when they are inside
of a disabled <if>.

Review URL: https://codereview.chromium.org/11549036

git-svn-id: 50c90c531a9fd8f38831f054b7ea6b96f50d91dc@92 7262f16d-afe8-6277-6482-052fa10e57b1

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