Added missed IOException to Reader.read(char[] buf) and Reader.read(c…

[treblereel]

…har[] buf, int off, int len) methods

Fixes #9915

[niloc132]

To land this, we're going to need to mark these as technically API-breaking changes in 2.12 - it is possible that someone was relying on them not throwing these exceptions and so was skipping the try/catch.

First though we need to generate a 2.11 reference jar, so we can see what changes might happen, I'll get that fixed soon.

[treblereel]

@niloc132 It's not worth it! Let's close this PR,

[niloc132]

No, that work should happen anyway, I'll get it done by the end of the week.

[niloc132]

Once #9982 merges, we can finish this finally - after that lands, merge with main, and make this change to fix CI:

diff --git a/tools/api-checker/config/gwt211_212userapi.conf b/tools/api-checker/config/gwt211_212userapi.conf
index 1279e029d8..ecd503d03d 100644
--- a/tools/api-checker/config/gwt211_212userapi.conf
+++ b/tools/api-checker/config/gwt211_212userapi.conf
@@ -149,4 +149,8 @@ excludedPackages com.google.gwt.core.client.impl\
 ##############################################
 #Api  whitelist
 # when adding to the white-list, include comments as to why the addition is
-# being made.
\ No newline at end of file
+# being made.
+
+# java.io.Reader missing IOException throws for read methods
+java.io.Reader::read([C) OVERRIDABLE_METHOD_EXCEPTION_TYPE_CHANGE new method has more exceptions: [Ljava/io/IOException;]
+java.io.Reader::read([CII) OVERRIDABLE_METHOD_EXCEPTION_TYPE_CHANGE new method has more exceptions: [Ljava/io/IOException;]