internal/lsp: unconditionally create changedFiles map

I don't think that creating it lazily was really buying us anything.

Fixes golang/go#41779

Change-Id: Ie19e1a62178a26744aca50cf6e40e380aed5afff
Reviewed-on: https://go-review.googlesource.com/c/tools/+/259618
Trust: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/internal/lsp/server.go b/internal/lsp/server.go
index daebcdf..5533b1b 100644
--- a/internal/lsp/server.go
+++ b/internal/lsp/server.go
@@ -26,6 +26,7 @@
 		delivered:            make(map[span.URI]sentDiagnostics),
 		gcOptimizatonDetails: make(map[span.URI]struct{}),
 		watchedDirectories:   make(map[span.URI]struct{}),
+		changedFiles:         make(map[span.URI]struct{}),
 		session:              session,
 		client:               client,
 		diagnosticsSema:      make(chan struct{}, concurrentAnalyses),
diff --git a/internal/lsp/text_synchronization.go b/internal/lsp/text_synchronization.go
index a806477..0a78114 100644
--- a/internal/lsp/text_synchronization.go
+++ b/internal/lsp/text_synchronization.go
@@ -284,9 +284,6 @@
 	s.changedFilesMu.Lock()
 	defer s.changedFilesMu.Unlock()
 
-	if s.changedFiles == nil {
-		s.changedFiles = make(map[span.URI]struct{})
-	}
 	_, ok := s.changedFiles[uri]
 	return !ok
 }