Prevent KotlinDecompiledFileViewProvider from reading vfile when possible

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/ClassFileDecompilerUtil.kt

@@ -49,12 +49,17 @@ fun isKotlinWithCompatibleAbiVersion(file: VirtualFile): Boolean {
  * Checks if this file is a compiled "internal" Kotlin class, i.e. a Kotlin class (not necessarily ABI-compatible with the current plugin)
  * which should NOT be decompiled (and, as a result, shown under the library in the Project view, be searchable via Find class, etc.)
  */
-fun isKotlinInternalCompiledFile(file: VirtualFile, fileContent: ByteArray): Boolean {
+fun isKotlinInternalCompiledFile(file: VirtualFile, fileContent: ByteArray? = null): Boolean {
     if (!IDEKotlinBinaryClassCache.isKotlinJvmCompiledFile(file, fileContent)) {
         return false
     }
 
-    val innerClass = ClassFileViewProvider.isInnerClass(file, fileContent)
+    val innerClass =
+            if (fileContent == null)
+                ClassFileViewProvider.isInnerClass(file)
+            else
+                ClassFileViewProvider.isInnerClass(file, fileContent)
+
     if (innerClass) {
         return true
     }

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/KotlinClassFileDecompiler.kt

@@ -52,14 +52,8 @@ class KotlinClassFileDecompiler : ClassFileDecompilers.Full() {
             val virtualFile = provider.virtualFile
             val fileIndex = ServiceManager.getService(project, FileIndexFacade::class.java)
             if (!fileIndex.isInLibraryClasses(virtualFile) && fileIndex.isInSource(virtualFile)) return@factory null
-            val content = try {
-                virtualFile.contentsToByteArray(false)
-            }
-            catch (e: IOException) {
-                return@factory null
-            }
 
-            if (isKotlinInternalCompiledFile(virtualFile, content))
+            if (isKotlinInternalCompiledFile(virtualFile))
                 null
             else
                 KtClsFile(provider)