Fix unconditional warning in JS compilation with sourceMap disabled.

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/DefaultValues.kt

@@ -51,7 +51,7 @@ open class DefaultValues(val defaultValue: String, val possibleValues: List<Stri
     )
 
     object JsSourceMapContentModes : DefaultValues(
-            "\"${K2JsArgumentConstants.SOURCE_MAP_SOURCE_CONTENT_INLINING}\"",
+            "null",
             listOf(
                     K2JsArgumentConstants.SOURCE_MAP_SOURCE_CONTENT_NEVER,
                     K2JsArgumentConstants.SOURCE_MAP_SOURCE_CONTENT_ALWAYS,

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinJsOptions.kt

@@ -51,9 +51,9 @@ interface KotlinJsOptions  : org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
     /**
      * Embed source files into source map
      * Possible values: "never", "always", "inlining"
-     * Default value: "inlining"
+     * Default value: null
      */
-     var sourceMapEmbedSources: kotlin.String
+     var sourceMapEmbedSources: kotlin.String?
 
     /**
      * Prefix for paths in a source map

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinJsOptionsBase.kt

@@ -64,9 +64,9 @@ internal abstract class KotlinJsOptionsBase : org.jetbrains.kotlin.gradle.dsl.Ko
         get() = sourceMapField ?: false
         set(value) { sourceMapField = value }
 
-    private var sourceMapEmbedSourcesField: kotlin.String? = null
-    override var sourceMapEmbedSources: kotlin.String
-        get() = sourceMapEmbedSourcesField ?: "inlining"
+    private var sourceMapEmbedSourcesField: kotlin.String?? = null
+    override var sourceMapEmbedSources: kotlin.String?
+        get() = sourceMapEmbedSourcesField ?: null
         set(value) { sourceMapEmbedSourcesField = value }
 
     private var sourceMapPrefixField: kotlin.String?? = null
@@ -117,7 +117,7 @@ internal fun org.jetbrains.kotlin.cli.common.arguments.K2JSCompilerArguments.fil
     noStdlib = true
     outputFile = null
     sourceMap = false
-    sourceMapEmbedSources = "inlining"
+    sourceMapEmbedSources = null
     sourceMapPrefix = null
     target = "v5"
     typedArrays = true