Make google-java-format friendlier to TSAN

This code does deliberate racy initialization of some memoized values,
and there is a static final instance of the `Space` subclass that ends
up being shared across multiple threads.

Tested: sponge/1777b644-2dd8-420b-ad06-b4f17c893d8f
PiperOrigin-RevId: 563181626

Author: cushon

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

@@ -19,13 +19,15 @@
 import static java.lang.Math.max;
 
 import com.google.common.base.MoreObjects;
+import com.google.common.base.Suppliers;
 import com.google.common.collect.DiscreteDomain;
 import com.google.common.collect.Iterators;
 import com.google.common.collect.Range;
 import com.google.googlejavaformat.Output.BreakTag;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
+import java.util.function.Supplier;
 
 /**
  * {@link com.google.googlejavaformat.java.JavaInputAstVisitor JavaInputAstVisitor} outputs a
@@ -102,28 +104,21 @@ public String toString() {
   private static final DiscreteDomain<Integer> INTEGERS = DiscreteDomain.integers();
 
   // Memoized width; Float.POSITIVE_INFINITY if contains forced breaks.
-  private boolean widthComputed = false;
-  private float width = 0.0F;
+  private final Supplier<Float> width = Suppliers.memoize(this::computeWidth);
 
   // Memoized flat; not defined (and never computed) if contains forced breaks.
-  private boolean flatComputed = false;
-  private String flat = "";
+  private final Supplier<String> flat = Suppliers.memoize(this::computeFlat);
 
   // Memoized Range.
-  private boolean rangeComputed = false;
-  private Range<Integer> range = EMPTY_RANGE;
+  private final Supplier<Range<Integer>> range = Suppliers.memoize(this::computeRange);
 
   /**
    * Return the width of a {@code Doc}, or {@code Float.POSITIVE_INFINITY} if it must be broken.
    *
    * @return the width
    */
   final float getWidth() {
-    if (!widthComputed) {
-      width = computeWidth();
-      widthComputed = true;
-    }
-    return width;
+    return width.get();
   }
 
   /**
@@ -133,11 +128,7 @@ final float getWidth() {
    * @return the flat-string value
    */
   final String getFlat() {
-    if (!flatComputed) {
-      flat = computeFlat();
-      flatComputed = true;
-    }
-    return flat;
+    return flat.get();
   }
 
   /**
@@ -146,11 +137,7 @@ final String getFlat() {
    * @return the {@code Doc}'s {@link Range}
    */
   final Range<Integer> range() {
-    if (!rangeComputed) {
-      range = computeRange();
-      rangeComputed = true;
-    }
-    return range;
+    return range.get();
   }
 
   /**