8155259: Suspicious buffer allocation in com.sun.tools.javac.file.BaseFileManager

8172106: javac throws exception when compiling source file of size 1.5G

Reviewed-by: vromero

src/jdk.compiler/share/classes/com/sun/tools/javac/file/BaseFileManager.java

@@ -432,7 +432,7 @@ public abstract class BaseFileManager implements JavaFileManager {
             ByteBuffer result =
                 (cached != null && cached.capacity() >= capacity)
                 ? cached.clear()
-                : ByteBuffer.allocate(capacity + capacity>>1);
+                : ByteBuffer.allocate(capacity);
             cached = null;
             return result;
         }