Handle odd data lengths in UTF-16 decoder

LayoutTests/fast/encoding/api/end-of-file-expected.txt

 Edge cases around non-fatal errors at EOF
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 
 PASS new TextDecoder('utf-8', {fatal: true}).decode(new Uint8Array([0xff])) threw exception EncodingError: Failed to execute 'decode' on 'TextDecoder': The encoded data was not valid..
 
-Should not throw or hang:
-new TextDecoder('utf-8').decode(new Uint8Array([0xff]))
+PASS new TextDecoder('utf-8').decode(new Uint8Array([0xff])) is '�'
 
-FAIL new TextDecoder('utf-16le', {fatal: true}).decode(new Uint8Array([0x00])) should throw an exception. Was .
+PASS new TextDecoder('utf-16le', {fatal: true}).decode(new Uint8Array([0x00])) threw exception EncodingError: Failed to execute 'decode' on 'TextDecoder': The encoded data was not valid..
 
-Should not throw or hang:
-new TextDecoder('utf-16le').decode(new Uint8Array([0x00]))
+PASS new TextDecoder('utf-16le').decode(new Uint8Array([0x00])) is '�'
 
-FAIL new TextDecoder('utf-16be', {fatal: true}).decode(new Uint8Array([0x00])) should throw an exception. Was .
+PASS new TextDecoder('utf-16be', {fatal: true}).decode(new Uint8Array([0x00])) threw exception EncodingError: Failed to execute 'decode' on 'TextDecoder': The encoded data was not valid..
 
-Should not throw or hang:
-new TextDecoder('utf-16be').decode(new Uint8Array([0x00]));
+PASS new TextDecoder('utf-16be').decode(new Uint8Array([0x00])) is '�'
+
+Streaming cases:
+decoder = new TextDecoder('utf-16le', {fatal: true})
+odd = new Uint8Array([0x00])
+even = new Uint8Array([0x00, 0x00])
+
+PASS decoder.decode(odd, {stream: true}); decoder.decode(odd) did not throw exception.
+PASS decoder.decode(even, {stream: true}); decoder.decode(odd) threw exception EncodingError: Failed to execute 'decode' on 'TextDecoder': The encoded data was not valid..
+PASS decoder.decode(odd, {stream: true}); decoder.decode(even) threw exception EncodingError: Failed to execute 'decode' on 'TextDecoder': The encoded data was not valid..
+PASS decoder.decode(even, {stream: true}); decoder.decode(even) did not throw exception.
 PASS successfullyParsed is true
 
 TEST COMPLETE