Simplify RadioNodeList's anonymous indexed getter

Make RadioNodeList's anonymous indexed getter argument mandatory and drop
the [IsIndex] IDL extended attribute. 'optional' and [IsIndex] have no
effect on the generated code of anonymous indexed getters:
- There is no way for the caller to omit the index
- The generated code uses ObjectTemplate::SetIndexedPropertyHandler() and
the IndexedPropertyGetterCallback takes a uint32_t in argument.

There is no web-exposed behavior change, the generated bindings code is
identical.

R=haraken
BUG=237739

Review URL: https://chromiumcodereview.appspot.com/21891009

git-svn-id: svn://svn.chromium.org/blink/trunk@155535 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make LayerRectList's indexed getter consistent with other indexed getters

Make LayerRectList's indexed getter consistent with other indexed getters:
- The argument is now mandatory
- We no longer throw if the argument is negative (dropped [IsIndex])

This is an internal interface and it has not impact on the existing layout
tests. This is one step towards completely removing [IsIndex] Blink-specific
IDL extended attribute.

R=haraken
BUG=237739

Review URL: https://chromiumcodereview.appspot.com/22184006

git-svn-id: svn://svn.chromium.org/blink/trunk@155536 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Check updating attribute when set timestampOffset for SourceBuffer.

Error should be thrown when try to set timestampOffset for pending sourceBuffer.

BUG=239506
TEST=Updated http/tests/media/media-source/mediasource-append-buffer.html LayoutTest.

Review URL: https://chromiumcodereview.appspot.com/21207002

git-svn-id: svn://svn.chromium.org/blink/trunk@155537 bbb929c8-8fbe-4397-9dbb-9b2b20218538