Don't crash on empty type declarations.

JLS 7.6 says:

> Extra ";" tokens appearing at the level of type declarations in a compilation
> unit have no effect on the meaning of the compilation unit. Stray semicolons
> are permitted in the Java programming language solely as a concession to C++
> programmers who are used to placing ";" after a class declaration. They
> should not be used in new Java code.

The formatted output for this is not pretty, but we don't care.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=106540484

Author: cushon

core/src/main/java/com/google/googlejavaformat/java/JavaInputAstVisitor.java

@@ -329,6 +329,8 @@ private static final ImmutableList<Op> forceBreakList(Optional<BreakTag> breakTa
   private static final int MAX_FILLED_INFIX_LINES = 1;
   private static final int MAX_LINES_FOR_FORMAL_LIST = 1;
 
+  private static final int MAX_EMPTY_DECLS = 10;
+
   /**
    * The {@code Visitor} constructor.
    * @param builder the {@link OpsBuilder}
@@ -388,16 +390,25 @@ public boolean visit(CompilationUnit node) {
       if (!first) {
         builder.blankLineWanted(BlankLineWanted.YES);
       }
+      dropEmptyDeclarations();
       markForPartialFormat();
       type.accept(this);
       builder.forcedBreak();
       first = false;
     }
+    dropEmptyDeclarations();
     // set a partial format marker at EOF to make sure we can format the entire file
     markForPartialFormat();
     return false;
   }
 
+  /** Skips over extra semi-colon at the top-level, or in a class member declaration lists. */
+  private void dropEmptyDeclarations() {
+    for (int times = 0; times < MAX_EMPTY_DECLS; times++) {
+      builder.guessToken(";");
+    }
+  }
+
   /** Visitor method for {@link AnnotationTypeDeclaration}s. */
   @Override
   public boolean visit(AnnotationTypeDeclaration node) {
@@ -3166,6 +3177,7 @@ void addBodyDeclarations(
       boolean first = first0.isYes();
       boolean lastOneGotBlankLineBefore = false;
       for (BodyDeclaration bodyDeclaration : bodyDeclarations) {
+        dropEmptyDeclarations();
         builder.forcedBreak();
         boolean thisOneGetsBlankLineBefore =
             bodyDeclaration.getNodeType() != ASTNode.FIELD_DECLARATION
@@ -3184,6 +3196,7 @@ void addBodyDeclarations(
       builder.forcedBreak();
       markForPartialFormat();
       if (braces.isYes()) {
+        dropEmptyDeclarations();
         builder.blankLineWanted(BlankLineWanted.NO);
         token("}", plusTwo);
         builder.close();

core/src/test/resources/com/google/googlejavaformat/java/testdata/B21647014.input

@@ -0,0 +1,15 @@
+package test;
+
+import java.util.List;;
+
+;
+class Test {
+  ;
+  public int x = 42;;
+  ;;;
+  {
+    int x = 1;;;
+  }
+  ;
+}
+;

core/src/test/resources/com/google/googlejavaformat/java/testdata/B21647014.output

@@ -0,0 +1,13 @@
+package test;
+
+import java.util.List;
+
+;;class Test {;
+  public int x = 42;;;;;
+
+  {
+    int x = 1;
+    ;
+    ;
+  };
+};