Leave 'linux' defined on x86/x86-64, like arm.

Change-Id: I53013a45c19a643a985de3f339b8b3f8f4dc39d2
Leave 'linux' defined on mips/mips64, like arm.

Change-Id: Idf1e781c34d45d1e20b7e5542d79201ae93668fe
Remove chromium_org and webview from the 64-bit blacklist.

external/chromium_org has been updated to handle 64-bit architectures
correctly in its makefiles; remove it from the blacklist so we can start
experimenting with building a 64/32 multilib version.

Change-Id: Ieb0e4f3cfea1578e01954c4656df90cd8d36b8cc
Merge "Remove chromium_org and webview from the 64-bit blacklist."
Merge "Leave 'linux' defined on mips/mips64, like arm."
Merge "Leave 'linux' defined on x86/x86-64, like arm."
auto-merger: merge in from aosp/master