Clear mLineWidths in LineBreaker::finish()

There was the possibility of stale indents from previous invocations
persisting in the mLineWidths across multiple invocations. This patch
clears them.

Bug: 28090810
Change-Id: I3621dfbe983512046289373711709aeade52eab4

include/minikin/LineBreaker.h

@@ -69,6 +69,9 @@ class LineWidths {
             }
             return width;
         }
+        void clear() {
+            mIndents.clear();
+        }
     private:
         float mFirstWidth;
         int mFirstWidthLineCount;

libs/minikin/LineBreaker.cpp

@@ -419,6 +419,7 @@ size_t LineBreaker::computeBreaks() {
 void LineBreaker::finish() {
     mWordBreaker.finish();
     mWidth = 0;
+    mLineWidths.clear();
     mCandidates.clear();
     mBreaks.clear();
     mWidths.clear();